Simple workaround: use Firefox instead. I also noticed instability and problems rendering pages in the default “web” app - but since I’m a Firefox user on other platforms anyway (GNU/ Linux Desktop and Android) it was not much of an issue for me. Firefox works quite well on the Librem 5 (I’m typing this reply using it, with an external Blutooth Keyboard).
I’d be interested comparing it to the “Web” app, though, once it becomes usable again. When Firefox is running the phone is getting warmer and the battery running out faster than when it’s not running, especially when having web.telegram.org open.
Another nuisance: when Firefox is playing an audio stream (a “podcast”) and I turn of the phone’s screen (to save battery) the audio starts stuttering. This does not happen with “proper” audio players like Lollypop or mplayer.