Being honest here - afaik there is no phone with pmos that has reliable voice phone calls.
So if you use your phone for calling think twice.
Fossman@as400 @khalid @postmarketOS I'm daily driving a #Librem5 with #postmarketOS and I've tested reliable voice calling successfully with multiple carriers in two counties. Also, tested with #PureOS.
Owners of older units may need to upgrade modem firmware and enable VoLTE manually. The real problem in my limited knowledge is carriers are blocking devices which are not on their 'approved list' or which they think are not VoLTE capable.
Another, bigger questions is: why are people still using unencrypted legacy voice calls for personal communications in 2026?