Packaging a GTK app as an click package is possible, but I could only manage to do so by giving the app special permissions (so this is a workaround and will most likely not be excepted in the official app store). Here is an example that worked on my Nexus 4 with Mir as the display manager and will maybe also work on other devices:
Video of working app (a simple image editor):
https://libre.video/videos/watch/2f2c5304-d278-4b43-84e0-3c463d3a6432
Source Code:
https://gitlab.com/AdamSchrey/image_and_buttons

Some of the things done here will maybe not be necessary on some devices or in future versions of Ubuntu Touch.

I had to add this lines to the .desktop file:
X-Ubuntu-Touch=true
X-Ubuntu-XMir-Enable=true

I had to add this line to the .apparmor file:
"template": "unconfined",

Otherwise I would get this error:
** (process:26446): WARNING **: Unable to exec '/usr/lib/arm-linux-gnueabihf/ubuntu-app-launch/xmir-helper image-and-buttons_0.9.0 ut_session.sh' in '/opt/click.ubuntu.com/.click/users/phablet/image-and-buttons': Permission denied

I had to export this variable to get bigger buttons/text/entries...:
export GDK_SCALE=2

To get an on screen keyboard I installed this packages on my device:
maliit-inputcontext-gtk3 maliit-inputcontext-gtk2

...and exported this variable:
export GTK_IM_MODULE=maliitphablet

I reply to this old post, because when I searched for a solution, this was one of the first things that came up and I could not find any working examples my self.
Maybe someone will find this helpful or will tell me if my app and my solution also work on other devices.

Some of the things I did, were taken from this website:
http://kriscode.blogspot.com/2016/09/x-applications-on-ubuntu-phone.html

Update:
I removed the proof of concept web app from the OpenStore, because I have no time right now to regularly restart the server or to fix the stability problems. It would also not make much sense to improve something, that will not be used.

It is all available under GNU GPL3 at: https://gitlab.com/AdamSchrey/open-store-payment-poc
So if anyone wants to revisit the idea, he/she can do so.
I am also happy to answer any questions about it.

Thank you all for the feedback

@doniks I thought the icon could be improved and created a different icon:

This is a png file. The original file is a svg file. It seems like the forum does not like svg files, so I made a merge request.
I did not like the low resolution of the current icon, this should not be a problem with a svg file.
If you still prefer the current icon, that is no problem.

Hello,
I wrote an app to compare the performance of different devices and released it on the OpenStore: https://open-store.io/app/ut-sysbench-qt-gui
I hope the arm64 version works, because I can only test the armhf version.
It would be nice, if some of you could share your device's name together with the results you get, after clicking on "Multiple Benchmarks".
"Export and Compare" will copy the results to your clipboard and show you a bar chart with the performace of other devices.

Multiple results from different persons for the same model are also useful.

You are also free to share problems with my app. I know that the memory (RAM) test does not work on all devices.

----------------------------------------------------------------------------------------
Results of my LG Nexus 4 with Ubuntu 16.04 OTA-19:

sysbench --test=cpu --num-threads=2 --cpu-max-prime=20000 run
57 events per second

sysbench --test=cpu --num-threads=8 --cpu-max-prime=20000 run
113 events per second

sysbench --test=memory --num-threads=4 run
Operations performed: 0 ( 0.00 ops/sec)
0.00 MB transferred (0.00 MB/sec)

sysbench --test=mutex --num-threads=64 run
total time: 2.4057s

@Appointed
About UT and desktop apps:
The goal of Ubuntu Touch is to be an secure and open source mobile OS, that can optionally also turn into a Desktop OS, when you connect the mobile device to a bigger screen, mouse and keyboard.
When the user is in the desktop mode of UT, he maybe wants to use classic Desktop apps and this is what Libertine is for.
So it is not the goal of UT to make any desktop app work on a smaller formfactor and without a keyboard and mouse. Of cause you can still try to do so, but that it is not scaling correctly is no surprise. The real issue are the other errors (some programs not opening or not working correctly).

@Appointed said in Usable phone display:

responsible

Libertine is not working perfectly, but UT is a community driven project. You and me are as responsible to make things better as everyone else. The code is all on GitLab and GitHub. The UT core team is happy for everyone who can help.

For a lot of people it was way more important to get Android apps working on UT and move to focal and this was accomplished. So Libertine not working perfectly is a result of prioritizement and lack of contributors and not because of responsibility.

@MV I don't have a Volla X23, but the scaling probably works similar on most devices.
The steps in the question are maybe already the solution for you:

https://forums.ubports.com/topic/9317/how-can-i-change-scaling-on-20-04-focal-without-ut-tweak-tool-and-without-reboot

... These devices (and maybe other devices) set the scaling in /etc/deviceinfo/devices/halium.yaml.

In this file I changed "GridUnit" to a more convenient value (i.e. 28 on FP3 and 18 on Lenovo).

To make these changes take effect it is not sufficient to just restart Lomiri with systemctl --user restart lomiri-full-greeter.service. You'll have to reboot the device...

@kugiigi said in OpenStore payment system discussion:

Anyway, my concern right now is what's in the poc app? I'm not accusing anyone but we are mostly people who met in the internet and what if people who tries the poc actually input their payment details? How secure is the site and what does it actually do? Sorry if this was a stupid concern. It's just the first thing that came to mind

Your concerns are very valid, but it is designed so that the user does not need to put any data from him/her into the app. The user will see an address and can use any Litecoin wallet (another program or website) to send something to this address.
The server for open-store-payment-poc will now check the block chain, if any payment went to the given address (the sender and receiver are unknown, but every transfer to every address is known to everyone, this is how the block chain works).

You will always get a new address, when you click on "Buy" (needs some time and maybe sometimes fails, because the server hardware is not the best and my code for this proof of concept could be improved, it should only show that it can work). But every address always points to the same wallet (in this case my wallet, but it could also be the wallet of someone else for some other app).

@kugiigi said in OpenStore payment system discussion:

There's just so many things involved and not just technical but also legal matters.

The main idea here is: The OpenStore would not need to process the the payment, because it is done by multiple third parties (people who mine Litecoin or who have Litecoin nodes) and the OpenStore only provides an address and looks if there is anything transferred to that address. But the developer would probably need to take care of legal matters as taxes when he receives Litecoin to his wallet or later transfers them into "normal" money.

And just to be clear: Litecoin was chosen here as one of many possible solutions, because it works and is well established. I could have also chosen Bitcoin, but the confirmation times and the fees are lower with Litecoin.

@doniks You're welcome and no problem

Here is a similar thread for CPU performance tests with sysbench: https://forums.ubports.com/topic/6750/ut-sysbench-qt-gui-compare-cpu-performance-of-different-devices

Result of the graphic test of my LG Nexus 4:

Maybe this has not been decided jet, but I would like to hear what would be the most likely scenario for the future:

Will the OpenStore support mobile friendly snap packages in the future?
Or will we have the OpenStore and the SnapStore preinstalled in future releases of UT?
Or will the SnapStore completely replace the OpenStore?

@Salah I saw your other post and the "hacky" way with remounting the file system is the way I would do it (https://forums.ubports.com/post/81981).
I recommend to back up your data and to enable adb shell access, before doing so (you can often still access your device over adb shell, even if the GUI is broken).
Please be aware that an OTA update could break your device, after you did some hacks, but it is probably unlikely after changing some icons.
I don't think UT/Lomiri looks for any icons in the home folder (but I could be wrong), so it is either the "hacky" way or someone adds code to the system (pull request on GitLab), that lets Lomiri look for icon packages in a folder like $HOME/.icons/ (similar to what gnome-tweaks does).

@domubpkm
Thank you really much.

The memory test shows the RAM speed and it is good to see that it works on some devices. So it is maybe not a problem with Ubuntu Touch and I maybe need to change the parameters, so that we get results on all devices.

The mutex test shows the speed of mutual exclusions (less time is better). Sometimes multiple processes want access to the same files at the same time and this access permissions need to be managed. This management is done by mutexes.

@UBportsNews
Currently Libertine is advertised as a solution for running classic Ubuntu X11 desktop apps on UT (something like this is mentioned when the first Libertine container is created). Unfortunately this is not working perfperfectly right now.
But as far as I understood it, snap packages coming to UT should make it way easier to run normal Ubuntu desktop apps on UT. Is that correct?
So, in the future, will Libertine become a solution primarily for classic Terminal programs (like vim, gcc and ranger) and will people install classic desktop apps (like Gimp and Libreoffice) as a snap, if possible? Or will most of the problems with Libertine be solved with updates to Mir and it will continue as the default way to install classic GUI desktop apps?

@Salah Maybe iteresting for hacking your device: All installed applications can be found under: /opt/click.ubuntu.com/
And the icons of the applications are often under: /opt/click.ubuntu.com/[AppName]/current/assets/

But if you install a new version of the app, any changes you do here will most likely be gone.

@messayisto Yes, thank you. This helps to confirm, that the test result of the app is not comparable between different OS versions.

Just to be sure: You also did not turn the screen of your device off when the test was running?

@_Joao_ The Mimi Browser worked for me with the DDG AI even after closing and opening it multiple times. If it still does not work for you after restarting your device, you could delete ~/.cache/mimibrowser.fredldotme and/or reinstall Mimi Browser (this will probably delete all your browser settings).