I wouldn’t do Ubuntu Touch on the P3a if you’re in an area where VoLTE is required. It seems this model is too old to get the treatment it needs.

Ubuntu Touch doesn’t officially support it yet, but it is working reliably for several phones now.

I daily drive Ubuntu Touch on a Fairphone 5. It’s not without quirks, but I like the experience. Many practical and nice native apps, Android app support through Waydroid, banking and things that would require Google Play verification I solve through the browser. Fairly good battery life, VoLTE is solved for the FP5 and some other models (which has been an issue with many Linux phones) and the community is very active solving issues and helping each other day and night.