repro is the SIP proxy from the reSIProcate project.
It has the following key features that make it highly desirable as the core SIP server in any Ubuntu VoIP/RTC deployment:
out-of-the-box support for Federated VoIP
an easy to use web-interface (see screenshots)
support for mutual TLS authentication - guide to setting up mutual-TLS (client certificate) authentication with Jitsi
To get support with repro on Ubuntu, users are welcome to come and ask questions on the repro-users mailing list
WebRTC support is expected in v1.9.0 of repro.