I agree that it seems very weird, but as a user all I know is that the exact same steps that works using Xorg does not work using Wayland.

And as a user, that's all I care about.

edit: This time might be SMPlayer, last time was perhaps Firefox, and so on. I've tried Wayland at least once a year for ages, and every single time I have to go back because something is broken.

That issue really could be anything, it could be something you did like putting some credentials in X-specific config files, or it could be SMPlayer looking for some X configuration that isn't there...

As I mentioned, I did reconnect to the share while in Wayland, and I did it as I have in Xorg, using the file explorer. So if that's the issue, it's the file explorer and not SMPlayer. Though SMPlayer logs did mention Wayland and authentication error on the same line... so clearly SMPlayer is doing something different in Wayland.

But sure, it could be anything. All I know is if I select Xorg on the login screen things just work, and when I select Wayland things don't.

To make any further investigation, you would have to share the error message.