@ck @fdroidorg @IzzyOnDroid If you are using #CalyxOS, there is also a sip client baked into the dialer. Sorry I don't know if the dialer is available stand alone.
My experience with all three of these though (Baresip, Linphone, Calyx Dialer) is that they will murder your battery if you use them in an "always available" setting. (Ie keeping a web socket open)
Balsillie family social hub.