I guess this happens in many games, making the workshop useless. I was playing Left4Dead2, and the addons or mods don't work, steam flatpak is the only way I have to play, because the he Native Steam doesn't run games well, FPS are unstable.
Try making a different steam library folder and whitelisting it in flatseal. I heard this only happens with the default steam library folder that flatpak uses.
I guess this happens in many games, making the workshop useless. I was playing Left4Dead2, and the addons or mods don't work, steam flatpak is the only way I have to play, because the he Native Steam doesn't run games well, FPS are unstable.