Ever since this Manjaro ARM Beta 17 with Phosh (PinePhone) - #31 by varikonniemi i have again had minor problems with it on phosh, like needing to go to settings and turn off and on the mobile data to get it back working. On plasma it is done automatically, so the only sign is deactivated and activated messages in notification center.
So there clearly is still stability problems with the modem even using open firmware, but it seems to recover correctly and automatically now, and phone calls and receiving text works fine, i have not tried send one yet, but i never had problems with texts, not even a year ago.
I also like the power savings of the firmware, which can be felt as reduced heat on the back cover.