New comment by Johnnynator on void-packages repository

https://github.com/void-linux/void-packages/issues/14251#issuecomment-529167159

Comment:
The Telegram notification thingy is broken in sway without any additional rules in your sway config, the easiest way to workaround is to install libnotify (and gtk3) and install a notification manager like mako.

The 2nd issue seems to be the picture viewer being broken probably.
edit: Clicking on images does bring the image viewer up as intended for me.