Thanks for the tip! That did the trick!
These are examples of the Keepassxc snap compiled with base: core18 & qtwayland5; with DISABLE_WAYLAND=1 (using Xwayland I guess):
And with no variable set (using Wayland-EGL):
And those are the messages I get when doing the latest:
$ keepassxc
QSocketNotifier: Can only be used with threads started with QThread
Using Wayland-EGL
EGL not available
Cannot find EGLConfig, returning null config
Using the 'xdg-shell-v6' shell integration
...