VoWifi / Appels Wi-Fi Galaxy S9

I remebered reading something about vowif being unavailable for Samsungs on Lineage based devices but couldn’t find the conversation. However there is this post that may provide some insight:

If it was available there should be a setting in Settings > Network & Internet > SIMs.

Another check can be made in “phone info” in the dialer, just dial ##4636## and select phone information.