Reason: un-def supports booting on RPi4.
lts kernel flavour has not been updated for a long time.

Variable SPECIAL_USER must have the following format:
user:group:uid:gid:homedir:shell
Example:
@$(call set,SPEC_USER,user:user:500:500:/home/user:/bin/bash)

This is consistent with other architectures.

these targets support all Raspberry Pi.

slick-greeter is well integrated with cinnamon.

+systemd-optimal do not call +systemd more.
Also added +systemd-optimal into jeos-systemd, regular-server. Need
to disable core dump

rootfs is not required to be installed on lvm2.

mpv is not needed in every single one of those images.

Use polkit-sysvinit as a workaround.

See-also: https://lists.altlinux.org/pipermail/devel/2019-November/208963.html

Reverts: 08d93ed8
(and several slightly more involved places)

Xfce used to present artifacts with compositing disabled;
now that it's fixed compositing can be disabled to increase
performance.