What about the installation commands with the new versioning schema? Are these still applicable?
sudo -u homeassistant -H -s
source /srv/homeassistant/bin/activate
pip3 install homeassistant==0.XX.X
will replacing “0.XX.X” with “2020.12” still work for upgrading to a specific version?
Moreover, what about Python 3.7 support? Is it still compatible or not?
Thanks
Yes, at least if you use a valid release number, which that isn’t quite 
See https://pypi.org/project/homeassistant/#history
AFAIK 2020.12.x is the last version that’ll support 3.7. You should use this as an opportunity to build a venv on 3.8.7, or if you’re feeling adventurous 3.9.1.
Should be 2020.12.0
Python 3.7 is still supported but I highly recommed updating now, sooner or later you’ll have to anyway and you’ll do this every year around December so you’d better get used to it.
Is there a reason you run it in a virtual env?
I have been running Home Assistant Core on a Raspberry Pi Zero for more than a year now, and despite its limited computing power it does a great job.
On the Raspbian version it’s running the Python version installed is 3.7.
I need to understand which is the safest option to upgrade Python. I think I could either upgrade Raspbian (or manually upgrading Python (but I still have to find a step-by-step tutorial on this), but I need to understand what this will break. It’s a pain to make everything working again from scratch.
Also, I will have to migrate the HA Core installation from the Python 3.7 venv to the new one in Python 3.8: any tutorial on this?
There are guides, but I’d 100% recommend you simply switch to using Docker. Then you don’t have this problem ever again.
Otherwise, see this guide for installing Python and creating a fresh venv. On a Pi Zero it should only take a day or so.
I’ll try your suggestion, thank you