I am having this issue with Strawberry. Kvantum will not work with it. Apparently the app can't see it.
But all my other Flatpak apps can find the Kvantum style.
I try this in the terminal:
flatpak run --env=QT_STYLE_OVERRIDE=Kvantum --filesystem=xdg-config/Kvantum:ro org.strawberrymusicplayer.strawberry
And I get this when the Strawberry starts:
09:34:19.914 WARN unknown QApplication: invalid style override 'Kvantum' passed, ignoring it. 09:34:19.914 WARN unknown Available styles: Windows, Fusion 09:34:19.928 DEBUG main:213 Style: "fusion"
Is there a fix for this?