i validated the quectel EM06 modem (in my case -E version for europe) in MNT Pocket Reform, also for voice calls. i don't have the extra SAI audio lines wired up yet in our imx8mplus mezzanine card, but i can call the Pocket Reform on my phone and play DTMF tones and the modem recognizes those. i can also call my phone via ATD commands etc. (all of this i only tested manually with AT commands, it's still like in 1997)

@mntmn https://forums.puri.sm/t/update-mar-25th-testing-quectel-em12-g-wwan-4g-modem-on-librem-5/19683 if i send you a EM12-G would you like to give that one a try as well? I was never able to get it to work myself but maybe things have changed on the driver or kernel support side.