SPA's have a bit of a reputation for being a bit flaky. The last generation I used was the old SPA3102 which is going back some years now. I still have the original (and a fresh spare in a box) which was routing PSTN into Asterisk (FXO) and taking then acting as an SIP extension ATA onto a cordless base (FXS).
Since then the landline disappeared, pure SIP trunks, went over to DECT on the domestic phones and used a couple of N300A IP Gigaset's across properties but talking back to an Asterisk box. This trusty old thing has been running solid since 2012 and the version of Asterisk (12) and Centos (6) have both been EOL and are long overdue an upgrade. But it has worked faultlessly over VM cable, 4G, 5G, FTTP, leased line you name it its done it.
Edited by Pheasant (Thu 01-Apr-21 12:23:48)