> Stretch also goes end of life on June 30 2022, so just a few months away. You definitely shouldn't be using that.
The platform is part of the Python binary packages build chain; they are purposely on the old side of the spectrum in order to create binaries which can work with as many Linux distributions as possible, making use of core libraries ABI compatibility. The rationale is available at https://peps.python.org/pep-0513/
Ah yeah, that makes sense. Then buster is likely the better choice, yeah. (But you do want to get off stretch before it goes into unsupported land)