How to force an application to run in Xwayland instead of Wayland

I had a problem with the game osu!lazer in Fedora KDE Wayland today. I know how to force a flatpak application to run in Xwayland, but this was an AppImage.

This command fixed the issue:

env -u WAYLAND_DISPLAY ./osu.AppImage

So, to force a non-flatpak application to run in Xwayland, simply type in the terminal (or modify the launcher):

env -u WAYLAND_DISPLAY <insert-name-of-application>

For flatpak applications, it's a bit different.

Download Flatseal from flathub, change permissions of your application or game in Flatseal to remove the "Wayland" socket. In my experience, in versions of KDE lower than 5.23, you might need to disable "fallback-x11" socket as well.

How to fix ugly/jagged fonts in flatpak GTK applications in Fedora 35 KDE wayland

The fonts in GTK/Gnome flatpak applications in the Fedora 35 KDE wayland session currently look like garbage (they are not antialiased) unless you run them without the wayland socket. This is due to xdg-desktop-portal-gtk being built incorrectly. You can fix this by installing xdg-desktop-portal-gnome and rebooting.

Step 1. sudo dnf install xdg-desktop-portal-gnome

Step 2. Reboot

Step 3. Verify that xdg-desktop-portal-gnome is running instead of xdg-desktop-portal-gtk

Fonts in flatpak'ed GTK/Gnome applications should look fine now.

See these bug reports for more details:

https://bugzilla.redhat.com/show_bug.cgi?id=2012315

https://github.com/flatpak/xdg-desktop-portal-gtk/issues/355

https://github.com/flatpak/flatpak/issues/4438