This approach is okay if you can work entirely in an environment (venv or otherwise) that is unmoored from the underlying system. But usually the reason to use an older OS is because you want to be linking to specific versions of boost or some other dependency that's a pain to build and install from source, so depending on your scenario, installing a deadsnakes python may not work if you're depending on there being a corresponding `python3-xxxx` package that links up system python to bindings for a particular library.
