built a copy and paste tutorial to install Python 3.9 that allows Home Assistant to install
This is intended for a Bare metal reinstall of your OS
Home Assistant Friendly Python 3.9
and if you used this tutorial to build your Home Assistant then it is real easy to copy all the Home Assistant files to another location and re paste them once you redo your Home Assistant with 3.9
nice and clean
Installing Home Assistant with File Sharing