Thanks for this info! I spun up a VirtualBox of Debian13 and was able to run the app and export characters so I don’t think it’s Debian13 itself.
I think the issue might be related to this Godot Plugin we’re using to open the OS filesystem when exporting a spritesheet: https://github.com/98teg/NativeDialogs
I’m going to try and switch to an in-app file viewer for exporting and see if that works better and if it does it will be in our next update! In the meantime maybe research if there’s any libraries you may be missing?