All right. I guess that you are not a developer yourself ? or at least not of the telephony part ?
So you don't have any clear information yourself, only second hand ?
If it is the case, could you at least try to make the devs understand that writing some information about the situation even if with all caveats apply such as 'it worked like this at this point of time' with no warranty about other versions and other providers known to work at this time, could be better than nothing ?
I think of the information asked for by @Lumpology, upgrading it at least one time by month or even per 2 months (even to say that nothing has changed) and at least updating this mystifying part:
Incoming, outgoing callsBugtracker
Calling over VoLTE is not supported, please check that this is not a requirement in your country.
Because well, for an open source project, asking people to get direct access at developers on a proprietary platform like Telegram is not very self conscious. If they want it, that's their call, but in this case they should take some care of giving information by other channels.
It's in the interest of the project because all quotes that can be given on the project state are on your web site, and at this time, anyone can pretend that the project is dying because it can't even support 4G telephony. If you have good news, give them officially so it can be cited, indexed on the Internet.
Thanks.