Comment # 3 on bug 1012272 from Dominique Leuenberger

At least on Tumbleweed this seems to work now:

I tried:
* https://flathub.org/apps/details/org.frozen_bubble.frozen-bubble
* Click install
* The 'open dialog' pops up, populated with 'install software'
* After confirming, gnome-software launches, allowing to install