You're seeing the same thing I see. I am on windows. I think basically the game just doesn't have any content yet. It has a few other maps/rooms you can walk around in, but as far as I can tell there is nothing else to do at the moment. I've been checking for updates every couple days, they'll pump something out for us eventually.
Heya!
Yes right now we are working on improving the game client, the project is open source and you can follow the progress of the next version here: https://gitlab.com/sourceofmana/sourceofmana/-/tree/godot4
We also discuss about it on our discord group, feel free to join us there!