Got hold of a Oneplus 6. Running Android 11, so downgraded using OB25 build from here.
Unlock the device (open developer options by tapping build in about device until it states "you are now a developer", back to System, Developer options, enable OEM unlock and USB debugging). In a command prompt use ADB to reboot to bootloader and then use the fastboot command "fastboot oem unlock", then when done reboot the device and set Android up again. Set up developer options and USB debugging, set it file transfer and copy the OB25 file to the root of the device (i.e. not in a folder). Go to system update and check local update and tap the zip file. Allow it to do its thing and tap reboot when done. The set android up again and hey you are on Android 9!
Then just follow the UT installer.
Installed so easily, I thought it was a Nexus 4 (apart from the Halium splash). Less than an hour and it is up and running. Good device so far!

I was messing around with Waydroid today with a spare two minutes and accidentally hosed UT. My fault being too impatient waiting for some thing to install so I stopped the process and rebooted the phone (yes idiot). Phone then sits on the powered by Android screen and no movement any further. Reinstalled from the installer as I couldn't get into recovery and my phone is back as is without having to reinstall apps or anything else. Took less than 10 minutes.
My point is if you are a newbie to this and something goes wrong, all is not lost.
Although, Waydroid is gone - no loss to me as I used it for interest only. The Waydroid helper is really good.

@dtarrant There is a lot going on with the development channel that is causing issues. Unless you are prepared to soft brick the device for testing things out, it is best to stay on stable or release. I only go on development when I have more than one device.

Really nice tablet. First thing I did was unlock the bootloader. You have to go into settings and push the button for OEM unlock, and USB debugging, boot to the bootloader (USB debugging =
./adb reboot bootloader). In the boot loader the installer instructions are wrong it should be:

./fastboot oem unlock-go

It is a bit hit and miss but persevere. Then reboot, it takes an age to restart so be patient.
Once back into Android, set USB debugging in developer mode and reboot into the bootloader.
Follow the on screen instructions, but this is very important:
Make sure you select developer or RC, NOT stable.
Again it will take a while, but you will get to "desktop" and it looks really good.

For some reason mine started in windowed mode, but I installed the UT tweak tool and it looks just as good in the staged mode.

So far it is really good and just what I want in a Linux tablet as all seems to work (I have Linx 1010b tablets based on the Atom Z series running Ubuntu 20.04 which are fine, but some things don't work).

Thank you to Luksus for the port.

(Unlocked and flashed from a Windows 11 machine on a USB 3.0 port)

Edit: 19th August 2022 - I have installed it with stable and the install using the latest UT installer wnet really well. Thank you for the heads up @Luksus on the OTA-23 update install.

With the fevered upgrade to 20.04, would it still be possible to have the installer and app store available so that older devices can install UT 16.04 and install apps? I don't want to see UT go the way of Android and iOS in orphaning devices and apps - it is one of the main reasons I started and now come back to UT.

If the 20.04 upgrade goes through would it be so far behind, Ubports Foundation would be working to develop UT on the next or latest LTS version?

I asked this question in Q&A, but probably due to time constraints it wouldn't be answered. Being into the device repair, I see a lot of issues so:

Would it be possible to add hardware issues to the devices information to assist users in the choice of hardware that they are going to purchase?

Examples are:
Nexus 5 irreparable boot loop unless you have a re-flow machine, even then not guaranteed to work.
Nexus 7 (2013) both versions - screen issues usually motherboard. USB port charging issues.
Nexus 4 - very common to have the lower touchscreen not working which requires replacement
SONY phones may not be able to unlock the bootloader - very common
Xiaomi phones - difficult to unlock the bootloader as you have to do it through their Mi Unlock program. If you are unlocking more than one you may have a long wait (up to a month per phone) and there is no work round (that I have found that works).

Also as a side note a lot of devices have battery life issues which is usually down to the age and previous usage of that device, not always Ubuntu Touch (Nexus 4 and 5 with batteries dating back to 2013 are OK, must have been well made!)

I know things are changing now so devices will be left behind, but it would be helpful for some of the potential pitfalls on devices. Main things could be:

1. Battery life
2. Battery replacement
3. Screen issues
4. Ease of unlocking

and so on. The older the device, the more difficult the parts to get are, and also the cost may rise so their is a lot of making a working device from four or five broken ones. I also understand that being a UT forum a big emphasis is on the porting side, but if you want to encourage new blood, and that person may have an unused phone that they want to mess things, this information would be helpful.

@domubpkm yes, it works and I have flashed many phones with 22.04.

It gets my vote. I have written to our Government (not EU any more) regarding this as we as a world human population have to stop putting perfectly viable electrical and electronic equipment into landfill. Apple and Samsung in the electronics industry are two of the worst publicly known offenders as their drvices orphan so quickly - even though they say they don't orphan devices and their devices are repairable (not).
This is one of the main reasons I think UT is the way forward - a community driven project that captures a small portion of the devices that would be disposed of as they are orphaned.
All hardware drivers should be open source so they can be integrated into the like of UT, Sailfish and others. Bootloaders should be easily unlocked. Hardware should be easily replaceable and repairable.

@flohack I guess it works for some and not others.

@saveurlinux yes, make sure you choose that one to install. I made the mistake of using a different one and UT would not install.

@maisumusuario Ok, it looks like you have two SIM cards in. Switch phone off and take one out. Start it up and try again, just follow the instructions - make sure mobile data is on.

@maisumusuario What is the error you are getting?

@gandalf I don't have a Fairphone, but this has never happened on any of my devices. It will most likely be down to the proximity sensor.

@opolork Have you rebooted the device and then cleared the browser cache? Have you removed and reinstalled the browsers? Have you checked for updates?

@mw4jet Yes, I have had to do it on some devices to get UT working (mainly OP3 and some Xiaomi devices). If Android works as it should, i.e. no ghost dialling and buttons work fine, then there is an issue between the device and UT.

Sorry, typing this on a phone.... The battery issue on UT is another thing that affects a range of devices, bearing in mind the age of the device etc.

But if someone at some stage in your devices live has had the screen or internals changed, it may throw up the ghost touch and buttons issue.

If you want to get to the bottom of the issue, sometimes you have to start from scratch, and that is unfortunately reinstalling the correct Android stock ROM and testing it on that to make sure the hardware functions. Then go back and install UT.

@ian You should be able to press the power button for a second to switch off the screen and put the phone to sleep. If that fails to work, it is usually a hardware issue, unless it has been altered within the software to alter the function of the power button (i.e. camera shortcut).
I have found if the phone is asleep, pocket waking doesn't happen unless you get a message or email or incoming phone call. To get an accidental emergency dial has never happened to me and shouldn't happen in any case.
From what @mw4jet described, it certainly sounds like a hardware issue - I could still be wrong, but from past experience if Android runs fine, but UT doesn't a reinstall fails, go back to square 1 and start with the stock Android ROM.

@triguy Hi, make sure T-Mobile is set to allow MMS (same issue on my carrier, quick online chat resolved). Double check the settings are correct and make sure 4G is enabled with data on.

@mw4jet Usually you will get these issues if the touchscreen has been replaced and/or the buttons for power and volume have been disturbed or damaged. If it doesn't have these issues in Android, there is a good chance Ubuntu Touch doesn't like something in the hardware. To test you will have to install the stock ROM and have a good play with the phone. If all is good, install UT again, following the install instructions to the letter. If UT repeats the issues, then you have incompatible hardware somewhere, which from my experience is usually the touchscreen.

@mw4jet Has the touchscreen ever been replaced?

@mw4jet No, did it t have the same nuances under Android?