This is likely an upstream issue. In my experience, qTox (all toxes?) has an echo on Debian and Fedora.

Please reconsider this. The policy requiring only new releases seems problematic. Plenty of Linux software is feature complete yet has not seen an update in the last two years. This is not tantamount to buggy or insecure or obsolete. Furthermore, Linphone has released a new version recently. Linphone is the only high quality softphone--far more update and robust than the heavy Jitsi SIP client that's been accepted. It additionally has a very useful command-line component that no other softphone of which I know has.