I added this edit above. Pasting here in case you are curious. Cheers.
EDIT: This thread motivated me to try and fix this issue. Installing Firefox using rpm-ostree worked. I expected it would, though I am still hoping to figure this out using the Flatpak version at some point. I also tried using Distrobox/Box Buddy to create a Fedora 40 box and install Firefox there. That version of Firefox couldn’t even see my NAS at all (unlike the Flatpak which could see my NAS but couldn’t upload files from the NAS to Proton). This was my first time ever using Distrobox. I thought it was super cool to see it in action and get a working Firefox, even though I couldn’t use it to access my NAS as hoped.
I’m playing through 4 now and I’m amazed at how good it looks. Very well optomized imho. It’s also a lot of fun.
I’ve never played the others but I would be tempted with a Steam release.