I tried out postmarketOS + phosh on a PinePhone about a year ago. For my own needs, it worked fairly well, except (ironically) receiving calls. It was like driving an old car, everything was slightly jank, but worked, and could be tinkered with - see the entire review. I have to give credit that there has been impressive progress in mobile Linux since PinePhone’s release in 2019, and a lot of it was developed by unpaid hobbyists.

Biktor and Lynxis will be working on OpenIMSd, which aims to bring VoLTE (4G voice calls) to Qualcomm based phones (like the PinePhone)

This is fantastic news, and I wish them all the best. Reliable VoLTE/WoWiFi calls was my main (but obviously major) issue with the PinePhone.

Another FYI: Ubuntu Touch does not support VoLTE at all, thus it might be more difficult to use it in some networks and countries (for example, USA shut down 3G some years ago)

However, I was pleasantly surprised by the responsive UI, the browser, and Cinny (the Matrix Client)

Fossify Messages and QKSMS/QUIK (unmaintained but has worked well for years)