Use the same dependencies and their order in both systemd units.
Add additional units of services that kodi uses.
Don't use "Requires=", kodi can run without a network connection.
Export WINDOWING=x11 in kodi.service to skip the autodetection that /usr/bin/kodi-standalone performs.
Give kodi-gbm.service the privileges of input group, this allows removing the kodi user from that group's membership since kodi.service does not need it.
Improve service description.
Use graphical.target, Xorg and graphical applications should only be started in graphical.target not in multi-user.target.
