Discord and TeamSpeak also use Opus, and Skype transitioned to Opus near the end. Opus became the de facto codec for phone applications over the past decade.
Particularly if you are using a SIP trunking service to reach any international destinations outside of the US50 states and Canada, it's going to be regular G.711 alaw or ulaw.
[1] I think they are called HD Voice+ in some market.