GtkRadiant Flatpak "Failed to load project file."

[GabrielDMorales]

Fresh install of GtkRadiant from Flathub on Ubuntu. I start up the program, point it at my Quake II steam directory, then click "start editor" and get this error when it tries to open:

"Failed to load project file. Please enter a valid project file."

I then get a file dialog box asking me to find a .proj. I have no project file, I want to start a brand new one. I can't get into the editor to start one. What can I do to continue?

EDIT: I managed to get the flathub version running by downloading the windows version, then running it with Wine, then creating a new project in my Quake II directory, then saving it, and then selecting it when I start the flathub version. It seems the problem is the flathub version needs a blank project to run.