Can't send ANY text messages using chatty, just shows red cross after a few seconds [update: upstream ModemManager bug]
For some reason I can't send any text messages using chatty on a PinePhone, it just shows red cross after a few seconds after I sent any (after showing a gray check mark for a few seconds) and I've asked the people I messaged to confirm it didn't arrive. Mobile data and receiving text messages works with zero issues, and I've received messages before with PostmarketOS+phosh+same cellular provider, albeit that being before a mainboard upgrade and a modem firmware upgrade.
PinePhone hw revision: whatever was sent out as upgrade, Manjaro or newer
Modem firmware version: EG25GGBR07A08M2G
Carrier: O2 Germany
Update: seems like it's this ModemManager bug: https://gitlab.freedesktop.org/mobile-broadband/ModemManager/-/issues/294 will update this ticket as new info becomes available