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!
I absolutely never trust blindly in such things. I have never seen a plausible explanation why this is a security feature.
When there are dev's from X11 involved, this is fine and it seems that this leads to decisions which prevent from current X11 issues. But it absolutely is no guarantee that everything is trustable. I'm not that expert, but your mentioned link points in the right direction. But as long this isn't supported in the wide mass, it's only a wish…