Telegram's problem with persian font

Solution 1:

There is similar topic in askubuntu question about telegram and its bad support for Persian language fonts.

A good news is that Telegram on newer release add default support to Persian with adding Vazir font family.

For you I suggest to remove telegram-desktop package if install with Ubuntu repository and download the latest one from official website to use latest update of telegram.

apt purge telegram-desktop

If you prefer more info on installing telegram in this method please read my answer on Iranian UBUNTU Community.