I see it has been reported already to HA forum HA supervised install on Debian bullseye brings cgroup and apparmor warnings - Installation - Home Assistant Community
Just to avoid a misunderstanding, DietPi is not an own OS. It’s a set of bash script on top of Debian.
Depending on SBC / manufacture, we use different kernel / configuration. Therefore, you need to be careful which guide you are using as there might be differences depending on SBC. The guide linked above is dedicated to RaspberryPi. Configuration shown inside guide will not work on NanoPi R5S as they use completely different kernel. The configuration file /boot/cmdline.txt even did not exist on NanoPi R5S. Therefore your adjustments done will have no effect.
Actually I’m not 100% sure where to adjust cgroup on NanoPi R5S, but maybe @MichaIng knows.
in general, it is possible to install Home Assistant Supervised on DietPi but depending on your SBC some tweak might be needed. Personally I did a test a couple of years back Home Assistant Supervised on DietPi - #8 by Joulinar