Ubuntu Touch was formally discontinued by them a few years back. It was rolled into the open source and is UB Ports. There are ports for a lot of phones, mostly older, and not all work 100%.
I am banking on the PinePhone. I have one and have been constantly updating it since it’s launch one year ago. There are currently a dozen linux builds for the phone, most in beta stage of development. It is not yet 100% functional. At the moment the Mobian (Debian Build), Manjaro Phosh and KDE and UB Ports (Ubuntu) are the most functional. They are still working on things like getting the device to wake from sleep, MMS Texting, and battery/OS Optimization. I predict that within 6 months it will be fully functional using linux. The Manjaro Linux with KDE is likely the best candidate as all KDE based apps should work with it.