I was looking at External Sites Module for nextcloud, which embeds an external site in an iframe inside nextcloud UI
Some time ago i was experimenting with doubango’s WebRTC2SIP Server and with their HTML5 WebRTC Client
Perhaps all this could be somehow mixed together and obtain a WebRTC Client, inside Nextcloud, which uses freepbx SIP extensions…
Ofcourse, as with all VoIP applications, this would need some fine tuning around security, NAT, STUN, QoS, etc…
Haven’t tested any of this, just some ideas