I'm looking for a good softphone in Linux. I tried Linphone, but it had the same issue I had in Windows where I could send texts ok, but can't send and receive calls. In Windows, I used Microsip since it worked as soon as I configured it. Linphone seems to be "special." Any suggestions?
On my Linux PCs, I ended up moving back to Linphone and adjusted some settings in my Asterisk server to work around the problems I had at first.
That said, I don't really use a softphone on my PC much these days. I re-purposed my old Android phones as SIP handsets. For ones that never leave the house, I just configured a SIP account in the native dialer and use UDP. For ones that need to work externally with TLS and media encryption, I use Sipnetic as my client.
Jmp.chat + gnome calls with SIP worked really well when I tried it. You could also try VoIP.ms and see if they have a SIP option
For sms jmp.chat uses Xmpp so any client should work. Xmpp clients can also do calls but they are not meant for phone number calls, though there are ways with JMP.chat/cheogram