References:
Install
sudo pacman -S firefox-i18n-pt-br
(Replace firefox-i18n-pt-br accordingly to your language or simply install firefox.)
In the installation dialog, select option 2) for pipewire-jack:
resolving dependencies...
:: There are 2 providers available for jack:
:: Repository extra
1) jack2 2) pipewire-jack
Enter a number (default=1): 2
The pipewire sound server will be automatically installed as a dependency (if needed).
Execute
firefox
Sound playback (including unmuting) should work out of the box. To test sound, go to www.youtube.com and play some music.