EDIT: Lol, it doesn’t actually work +___+ It is enabled in KeepassXC but it just doesn’t do anything. Welp.
Here’s a neat trick I just found out (with a hint from here):
In Wayland you can’t use KeepassXC’s very cool Auto-Type feature (it’s somehow Qt’s fault?) but if you installed it as a Flatpak you can go into KDE Settings, search for “Flatpak Permission Settings” and in the settings for KeepassXC under “Advanced” you can disable “Wayland Windowing System” to make it work. Nice!
Not having autotype is for me the reason not to switch to Wayland, too. I don't only have passwords for websites stored in KeepassXC - otherwise it wouldn't be a problem with the Firefox addon. Copy & paste of passwords into e.g. the console can't be better security. I wouldn't mind if autotype would work in general and one has to choose the corresponding entry manually without automatic matching to the current window. But even autotype into the last active window doesn't work.