I use VLC,Keepass,Kdenlive and few other QT Apps on my sway setup. So, wanted to configure their themes from Sway. I installed qt5ct and qt6ct and did export QT_QPA_PLATFORMTHEME=qt5ct in bashrc and .profile. While runnin echo $QT_QPA_PLATFORMTHEME it is showing qt5ct but it is not working showing that error message that QT_QPA_PLATFORMTHEME need to be set as qt5ct or qt6ct when launching from .desktop But when launching from terminal they start and function properly but do not change any theming.
A really common issue with sway is that it doesn’t run as a login shell, so none of your .profile or other environment settings get sourced when you login. I think that might be the problem here.
Try closing your sway session, then login to a tty and run
sway. If the qt themes work properly then it’s definitely an environment issue.