This has been a known problem for a very long time.
It would be really nice if a developer would comment if this is on some todo list or if they decided to ignore the problem.
I would like to note that the number of Threema users is constantly growing.
For me, it’s the most important app in my daily life, so I would be happy to know if they are working on this WebRTC issue or not. If it’s a clear no, I would consider trying LineageOS.