I had Xfce sound effects working from this discussion - Setting up Sound Effects
and toz on Archwiki - XFCE System sounds / Newbie Corner / Arch Linux Forums
The freedesktop theme didn’t work for me, but sound-theme-smooth from AUR works
Or the suggested Borealis theme can be downloaded and extracted to /usr/share/sounds/
https://dolys.fr/Dossier/Borealis.tar.gz