venv installed, mu-env created.
From within the mu-env dir, tried to ''''pip install matplotlib==2.2.2''' but it looks like it wants to use a cached version of matplotlib-2.2.2.tar.gz AND ended up with this error message:
'''WARNING: Discarding https://files.pythonhosted.org/packages/ec/ed/46b835da53b7ed05bd4c6cae293f13ec26e877d2e490a53a709915a9dcb7/matplotlib-2.2.2.tar.gz#sha256=4dc7ef528aad21f22be85e95725234c5178c0f938e2228ca76640e5e84d8cde8 (from https://pypi.org/simple/matplotlib/). Command errored out with exit status 1: python setup.py egg_info Check the logs for full command output.
ERROR: Could not find a version that satisfies the requirement matplotlib==2.2.2
ERROR: No matching distribution found for matplotlib==2.2.2'''
Also from within mu_env directory, tried to install python3.8.12 (last stable 3.8):
sudo apt install python3.8 1 ⨯
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
Package python3.8 is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
E: Package 'python3.8' has no installation candidate
I cannot find any documentation that says to do either of these tasks any other way than what I did, above.