Telegram Desktop
Telegram Desktop is available to be downloaded in postmarketOS from Alpine's repositories, and unlike what the name implies, it mostly works well on phones.
Tweaks
Sub-100% scaling
By default, Telegram Desktop may overflow and have some of its UI elements appear off screen. This can be worked around by settings a sub-100% UI scale. Unfortunately, Telegram Desktop's in-game settings do not allow for this, however the command-line switch `-scale` is offered for setting an arbitrary scale, for example:
$ telegram-desktop -scale 80
This will set the UI scale to 80%.
To make this permanent, you can copy the .desktop file into your home (this is to ensure that updates don't overwrite your changes):
$ cp /usr/share/applications/telegram-desktop.desktop ~/Desktop
Then open `~/Desktop/telegram-desktop.desktop` in your text editor of choice and edit the Exec line to include -scale 80 (or whatever scale works better for you). It should look something like this:
Exec=telegram-desktop -scale 80 -- %u