There must be GTK somewhere, gtk3 is a dependency on Arch and the GTK_USE_PORTAL env var strongly suggests GTK has something to do with the file chooser. If they’re going to have to reimplement the latter, I hope it’s going to be less horrible than the GTK one but knowing Mozilla I’m not that faithful…
I am THIS close to joining the Chromium monopoly gang (i.imgflip.com)