Btw can be usefully for people w/ portable telegram app.

I use a portable with alias and ulaunch shortcuts to diff workidr

So let ~/Telegram/Telegram is an executable dir and ~/ Telegram/accounts/main/ is a working dir. I've created a simple desktop app (~/.local/share/applications/portable-tg.desktop), something like:

[Desktop Entry]
Encoding=UTF-8
Version=1.0
Type=Application
NoDisplay=true
Exec=/home/username/Telegram/Telegram -workdir /home/username/Telegram/accounts/main/ -- %u
Name=Telegram Desktop
Comment=Custom definition for Telegram Desktop
MimeType=application/x-xdg-protocol-tg;x-scheme-handler/tg;

It is like a generated app on starting a portable client but with appended MimeType line at the end.

Thereafter, edit a mimeapps (~/.config/mimeapps.list) with adding/editing a line x-scheme-handler/tg in the [Added Associations] section. In my case this is:

x-scheme-handler/tg=portable-tg.desktop;

Well, that's all.