avs 
Just connected a 90-year old bakelite phone over VoLTE. Works đź’Ż
That machine was also once connected to ISDN, however briefly.
I’ve had a pulse dial capable SIP ATA waiting for some integration time for a decade. However, the modem I planned to use is now obsolete. But I found a ”voice” port behind my 4G/5G router and that relays calls over VoLTE! Just a pulse/DTMF converter (used Dialgizmo) and the Siemens & Halske (Reichmade) took to the airwaves.
The phone is my grandparents’, possibly their parents’, originally.
Alex@rtnVFRmedia Suffolk UK@avs From my experience you will likely have far better luck with that than SIP over LTE due to the amount of CGNAT and that the mobile companies rarely want to support it (especially in outer suburbs/rural areas where they seem to be struggling to keep LTE data working reliably as it is)
@vfrmedia Oh this isn't SIP from my equipment. This us VoLTE/VoNR, the native voice services which, albeit SIP under the hood, are now the primary voice services here as 2G is phased out