Since version 3.4.5, Rhythmbox dropped the mmkeys plugin, stating that
it is "no longer useful" and it "has been obsoleted by MPRIS". This
change broke the media keys support on i3.
Since the regression is on purpose, there might not be no way to get
this mmkeys plugin back in Rhythmbox. The workaround is therefore to use
MPRIS. I chose playerctl since it is the most straightforward to me. A
few i3 key bindings later, media keys were back in control of Rhythmbox!
https://gitlab.gnome.org/GNOME/rhythmbox/-/blob/v3.4.5/NEWS0cdeb7cb7ahttps://wiki.archlinux.org/title/MPRIShttps://i3wm.org/docs/userguide.html#keybindings
The default keys used to change focus were close to the ones used in
vim, but not the same, therefore being confusing. Because of that
they were not used and can be safely removed.
Furthermore, one of them is now mapped to the lock screen shortcut.
