First of all, I know that this has been brought up before and look like it did not start well.
So I want to suggest another approach:
Today, mozilla started to federate with other Matrix-homeservers and also opened up for registration on their homeserver - you can login with your existing Firefox account (nice right?)
So I suggest, that EndeavoursOS creates a room over at chat[.]mozilla[.]org instead of using matrix[.]org’s server.
After that room is done, we could quite easily bridge the room to the existing telegram chat - I suggest that we use the FENEAS bridge described here because it has been very stable since it launched in september + it is easy to get in touch with them if something would not work as it should. I also think that they would gladly help EndeavourOS too
And sorry for the weird links, new users are only allowed to post max two links in a post.