mautrix/telegram is a bridge between Matrix and Telegram. It mostly lets users of Matrix contact their friends who use Telegram. It is not a fork of Telegram and has nothing to do with the Telegram interface. (Note: OP wanted to use the Telegram client with a non-Telegram server. If you know of a Matrix client which looks and feels like the Telegram client, thats what theyre after.)

How is this relevant?

If your use-case is monitoring packets, why not go for an app made for that, such as Wireshark?

What is the format of these videos? Im afraid you wont get much compression out of conventional file compressors, as video files are usually already compressed to the point where you would have to reencode them to get a smaller file.

Im not sure how difficult it is to setup a Tailscale client, honestly.

The Zerotier setup is just installing and joining a network by an id. The Windows version has a bit of a GUI, where you have to right-click on a status bar icon, click Join network, paste in the id and join. The Linux version of the client has a cli, which is imho even better, as you can just send them a whole command to copy into the terminal.

I admin a Zerotier network for a bunch of kids that wanna play Minecraft, and they havent had many problems setting up.

There is a bunch of information on self-hosting the whole system, but Ive honestly never tried any of that. It was just nice that this was “just the open-source LogMeIn Hamachi with a superior implementation of everything”.

Can confirm, very easy to setup clients. And since its not a VPN but a VLAN, you wont run into problems connecting between different clients.

This is pretty much open-source Hamachi.

Which streaming service? I last used yt-dlp with the --live-from-start option on Youtube, it worked fine there.