What do you propose for - integration with telephony (so, yes a voip). 

There are some github projects - all i was able to find is old (like v14 od Odoo) or - somewhere there is a commercial licensing. 

I even saw a movie with a WebRTC (i preasume) on Odoo integrated calling and a SIP on the other hand - but - can't find any module ready to use id.

I do need a solution for an on-prem installation.