Install Home Assistant from scratch on an existing raspbian install
Install 2021-03-04-raspios-buster-armhf-lite.zip using balena etcher
Prepare the image as per usual pi installation
Make sure remote ssh is enabled
Hostname is set
Build Python3 from source. The version in the pi instance is too old
wget https://www.python.org/ftp/python/3.9.4/Python-3.9.4.tgz
tar xf Python-3.9.0.tar.xz
cd Python-3.9.0
sudo apt-get install libsqlite3-dev
./configure --enable-loadable-sqlite-extensions && make && sudo make install