Ah, I see! Yeah, a bigger catalog would be nice. You can add more repositories to it, enable Flathub, which provide more options, but something about it does feel hamstrung.
The Firefox thing is something I know about! You can set a config option in the about:config
page to tell Firefox to use your desktop’s standard dialogue. It has to do with XDG Desktop specifications, I think
Ooohh! Interesting. You’ve got me curious about that now. I’ll have to look into it.