It is most likely the xdg-desktop-portal-gnome.
You need to replace it with the package valid for your enviroment
Many applications (firefox, thunderbird, telegram, etc) slow to start on desktops other than Gnome
There is a bug with xdg-desktop-portal-gnome (more details here ).
Remove
sudo pacman -Rdd xdg-desktop-portal-gnome
Workaround for KDE
sudo pacman -S xdg-desktop-portal-kde
Workaround for gtk-based desktops (including Xfce)
sudo pacman -S xdg-desktop-portal-gtk
Workaround for KDE
sudo pacman -S xdg-desktop-portal-kde
Workaround for Lxqt
sudo pacman -S xdg-desktop-portal-lxqt
Workaround for desktops using hyprland
>sudo pacman -S xdg-desktop-portal-hyprland
Workaround for desktops using wlroots
sudo pacman -S xdg-desktop-portal-wlr