Successfully tested receiving #cellbroadcast messages on the #PinePhone as well:
# _build/test/mmcbmmonitor
[/org/freedesktop/ModemManager1/CBM/0] new cbm: received
4371: Hallo, this is a CBS test message
So hopefully all devices supporting `+CSCB` on an AT port should now be able to show these messages in @phosh (if the MR makes it into the next #ModemManager release).
The #osmocom stack is such a great help for testing these things.
Thanks to @NGIZero for supporting this.