I was having similar problems on a fresh arch install with multiple apps taking upwards of 15 seconds to launch, and the "fix" ended up being to uninstall one or more of the "portal" packages (there are several with names like xdg-desktop-portal-gtk). https://gitlab.gnome.org/GNOME/xdg-desktop-portal-gnome/-/issues/74 and https://bbs.archlinux.org/viewtopic.php?id=285334 for more info.

Could be completely unrelated, but it might be worth a try.

What desktop environment or wm are you using? Are you using a login manager or launching your session from tty?

I've had similar issues in the past but in my case I had to configure things so that when I log in it sets environment variables correctly and have my sway config start up xdg-desktop-portal correctly.

I've also had situations where specifically xdg-desktop-portal-gtk was causing problems so id uninstall that while keeping the other xdg-desktop-portal-* packages, so it could be one of those causing it

for anyone wondering a I fixed by deleting this directory ~/nvidia/GLCache/