I got an old LG Nexus 5 phone so I could finally try ubuntu touch on a phone. It's so called core device, which is fully supported by the ubports developers and all hardware should work. It has terrible battery life, but hey, its 3 years old with not replacable battery. I found pretty good install guide at ubports forum. It worked like a charm and all was done in 15 minutes.
Installation
My phone was in a factory default state with Android 6.0.1 (last update from Google for this device), so I switched it to developer mode. Located Build number item in Settings -> About device/phone and taped it 7 times.
I downloaded Magic-Device-Tool which is able to install ubuntu-touch on a phone. You can use: git clone https://github.com/MariusQuabeck/magic-device-tool.git to get it.
Then I booted my phone to the bootloader (fastboot mode) by pressing Volume up and down together with Power button. It stated, that device is locked.
So I used Magic-Device-Tool to remove a lock on my phone by starting launcher.sh (you select device, operation unlock and connect the device by USB, read carefully what is displayed in a console).
Then phone asked, if I really wish to do this and once confirmed, it wiped out all personal data and set itself to factory default again. On boot it shows Google logo with unlocked lock icon.
After the reboot, I rebooted again to booloader (fastboot mode) and run launcher.sh again to install ubuntu-touch OS to the phone (legacy chanel). It downloaded all necessary files and installed it to the phone in 5 minutes.
After a few more restarts it booted to ubuntu touch OS !!