Wen clicking a link in any application (not a browser), the application picker
asks, which application to launch. If chromium is selected, nothing happens.

Steps to reproduce
- Install MocroOS KDE
- Install Chromium flatpack
- Click link on any application to trigger x-scheme-handler/https 
- select chromium to open

Expected result: chrome opens the url
Actual result: nothing happens
Additional observation: chromium is not recognized as default browser
Solution: install xdg-desktop-portal-gtk - should this be part of the KDE
pattern?