I’d love to use my PinePhone (primarily) as a SIP client. Would you have any advice on suitable software that would adapt well to a mobile GUI?
Looking as well, managed to install Jami but so far didn’t managed to run, not sure what is the issue. Jami supports SIP as well as P2P.
Thanks for your suggestion. I appreciate it.
However, it seems like Jami will not be a solution for me. I need a SIP client to be connected to a local Asterisk server.
so far I didn’t managed to run Jami on the phone anyway 
Others on other devices I use linphone as a SIP client, I’ll probably check if it would be possible to get in on ARM linux as well.
Just FYI it looks like the reason why Jami does not run is only related to Phosh / XWayland issues, I had no problem to run it in Plasma.