Somewhat of a PSA for Qt users:

On Linux, Firefox will now default to the XDG portal file picker if available, rather than the GTK3 one, which is usually better integrated with the user’s desktop environment, and more powerful. https://www.firefox.com/en-US/firefox/149.0/releasenotes/

Edit: I talk about a patched version below, but it was an about:config toggle in more recent times.

Always needed a patched version of Firefox before for that. Presumably most distros will transparently throw that patch out of their Firefox package, so likely don’t have to do anything.

But well, you don’t specifically need a patched version anymore for that, so if that’s a separate package on your distro, you could consider using the normal package again. Although, I believe there’s also still patches floating about for using the KDE mimetype system…