I'm writing this on Ubuntu Touch running on a Raspberry Pi 3 using the OSK on the Pi 7" touchscreen.
Thanks for the hard work put in. There are some issues still of course. Something odd with the graphics in Pi 4 windows and a slight overlap on the touch screen making left or right swipes tricky but this feels so much closer to useable than the first image. I don't think it is too far now from a platform that will showcase convergence and perhaps even let us develop apps live. I appreciate this is a side project so the UBports developers can't make it a high priority. Hopefully though the work done will help towards getting other Arm64 non-Android ports running smoothly. As a long term Linux user - trying to help get Unity8 or UBports working on the Pi has been very humbling - I'd no idea how little I knew/know!

Re: Continuation of rpi effort and how to test
There was a mouse hover event bug that has been fixed upstream making selection with mouse and keyboard a vastly better experience - not perfect yet but much more useable. Worth trying again if you found it too frustrating before.
Wifi is now working on the Pi 3 and Pi 4. We are trying to sort out sound and Bluetooth - any help welcome.
Due to the pinephone and other arm64 devices most apps are available and have been updated to work.
One continuing bug seems related to content hub and Apparmor not working. This means that copying files or pictures between apps is not working (and leads to crashes at times).
Another cause of crashes seems to be related to windows on the screen. Try not to move or change size when a window is rendering and windows rendering over other windows can also cause problems.
The Pi has not got much ram so running multiple browser tabs and/or too many apps at once will lead to problems.
https://ubports.com/blog/ubports-blog-1/post/raspberry-pi-266
https://gitlab.com/ubports/community-ports/raspberrypi
https://t.me/UBports_pi

Is there a place where UT progress and dead ends with the Pinephone are being documented? I find there is so much posted in the Pinephone group on Telegram and a lot of it is not UT specific so I don't follow it as much as I should. I'd still like to know more and try to apply it to the Pi.

I realised that that post may look like I'm claiming some credit and that would be wrong.
Early on I did some blundering about in the dark and kept posting about my inevitable failures to encourage someone who knew what they were doing to help - that is the sum total of my contribution

@Flohack I have now updated the readme in a similar style to the Pinephone one and put in a merge request. Apologies if I've not followed the correct procedure - Gitlab is still new to me.

@advocatux Thanks - oh and apologies for re-opening a too old thread elsewhere

@Jules I have the same issue on the OPO (rc). Everything else seems to work as usual but I can no longer move the map by sliding with my finger. If I attach a mouse then it works fine scrolling as expected whilst holding down the left button and moving the mouse.

@Mark Sound now works (HDMI and audio jack) on recent images with a newer kernel. Apparmor can be made to work by making some kernel changes (copied from similar changes made for the Pinephone) but this is not yet in the downloadable image.

@Pulsar33 Sorry if I misled you. I used the title "Progress on the Pi 3". I'd added in that Wifi is working on the Pi 4 for information but perhaps I could have been clearer. You can access the Pi 4 using SSH (which is why I know the wifi is now working) but the graphics problem still needs someone with a lot more knowledge and skill than I have to fix it. You can log into the Pi 4 in spite of the graphics issue and a screenshot looks fine even if the actual display has all the feedback lines. However if you open an app in a window then do a screenshot the graphics problem can still be seen in the window on the screenshot.

@Flohack I have now updated the readme in a similar style to the Pinephone one and put in a merge request. Apologies if I've not followed the correct procedure - Gitlab is still new to me.

Re: Continuation of rpi effort and how to test
There was a mouse hover event bug that has been fixed upstream making selection with mouse and keyboard a vastly better experience - not perfect yet but much more useable. Worth trying again if you found it too frustrating before.
Wifi is now working on the Pi 3 and Pi 4. We are trying to sort out sound and Bluetooth - any help welcome.
Due to the pinephone and other arm64 devices most apps are available and have been updated to work.
One continuing bug seems related to content hub and Apparmor not working. This means that copying files or pictures between apps is not working (and leads to crashes at times).
Another cause of crashes seems to be related to windows on the screen. Try not to move or change size when a window is rendering and windows rendering over other windows can also cause problems.
The Pi has not got much ram so running multiple browser tabs and/or too many apps at once will lead to problems.
https://ubports.com/blog/ubports-blog-1/post/raspberry-pi-266
https://gitlab.com/ubports/community-ports/raspberrypi
https://t.me/UBports_pi

@Mark Thanks to the Q&A for kindly complimenting my contribution. I try my best to learn and share. From a distance it is hard to know how helpful that is. I'll keep on learning, sharing and appreciating the support I get from the community.
PS I need to make my questions shorter and clearer

Congratulations for all the work on the Pinephone and other Arm64 devices. One consequence of this is UT becoming more stable and useable on the Raspberry Pi. My question is: Where (website, group,book etc.) can I go to learn more so that when community members with good UT developer skills and knowledge come up with suggestions on how we might solve issues I have a better chance of knowing what they are talking about and how to start? Some things are making way more sense to me now than they did a year ago but I'd like to travel further down the linux user to developer road so my contributions are more helpful to the community.

On Pi 3 with touchscreen it starts without an external keyboard or mouse. The bug where you needed to unplug the mouse and plug it in again was fixed a long timealreadyThere are still niggling selection problems but lots of improvements. Good choice on the Openstore (though some apps still use oxide and ubuntu.web and they will need to be updated to work on the Pi). For me Dekko, Morph, TELEports, Openstore, Terminal, UT Tweak Tool, Document Viewer and many more work well already.

@Pulsar33 Several of us have a Pi 4 (mine is also 4Gb) but until someone (who knows how) can put in the work needed to get the tiling vs Unity8 problem fixed we can't get very far. However the more bugs and issues we can identify and fix on the Pi 3 in the meantime the better the Pi 4 experience will be when it comes.

I've tried image 117 and it seems to work as well on the Pi 3B+ as 95. It still has many of the same issues (wifi, selection and audio). Rodney helped fix the bug where the swipe tutorial covers the screen but won't disappear (because you can't swipe like on the phones).
If you only have a touchscreen and you find your view is getting blocked by the first run tutorial then edit /var/lib/AccountsService/users/phablet so that the line starting DemoEdgesCompleted reads DemoEdgesCompleted=[‘left’, ‘top’, ‘right’, ‘left-long’]
You can do this via ssh or (with difficulty) in the terminal squinting through the tutorial screen.
If you have an hdmi monitor and connect to that it should open in desktop mode and after that it will be fine in the touchscreen next time it is run.
The Super-a Key opens the launcher just like on Gnome.