Why is it so complex and difficult to install and maintain HomeAssistant?

The version working well for the Pi4:

Build Date: 2021.02.10
Release: 10 (Buster)
Family: 4
Tested Hardware: Pi4 (4GB)

you’ll find here.

Just note to run
sudo apt-mark hold linux-image-arm64
immediately after the first Login and before running
apt update && apt upgrade -y as I described here
and you should be good.

Also I advise you to strictly follow this excellent guide.

After the base installation of HA as per instructions install Samba, Portainer and MQTT by following @kanga_who guide again at https://github.com/Kanga-Who/home-assistant/blob/9f437fb0043daaa6ed450ed0eec7da479cb1ff93/Install Samba%2C Portainer and MQTT.md

I have used above guides a couple of times and they are working like a charm.