There are at least four standard ways of ensuring dependencies are met:
1. python package manager (pip) on top of the OS installation. Not nice since installs are OS wide.
(pip is itself a python package which we can assume is available as long as there is a python distribution installed ( after 3.something it's installed by default, otherwise it's trivial to install) )
2.
virtualenv. Per user, local installs in one directory, including specific python binaries, using pip. AFAIK the "venv" module is also included in python installs by default.
3. conda. Same as virtualenv but allowing for other binary dependencies (libraries).
miniconda is lightweight and pretty much a standard
4. containerised solutions (docker + first item in this list). Does not apply to our case.
IMO virtualenv is the way to go in TeXmac's case since it is itself a python package and we won't need any 3rd party libraries (non-python). But maybe someone else has another suggestion? I always do the fourth, so I rarely use virtualenv.
I'm afraid I really cannot help out now, I'm sorry :( Maybe in a couple of months..