German umlauts ä, ö, ü and ß are not recognized properly

Hi,

I installed this app a few days ago and it works great on X11 but unfortunately German Umlauts are not recognized properly. In most cases an `ü` becomes an `ii` and stuff like that. I guess the algorithm has to be changed to all UTF-8 symbols instead of only Latin characters.

I tested it on Ubuntu 24.04.3 LTS using the Flatpak installation method.