After a half day's work installing the dev Bela clone, python3 etc (following the script in the Wiki), I've come to the point, where the installation of heavy is required:

root@bela:~/Bela/hvcc# python3 -m pip install -e .
Obtaining file:///root/Bela/hvcc
Collecting Jinja2>=2.11 (from hvcc==0.5.0)
  Using cached https://files.pythonhosted.org/packages/7e/c2/1eece8c95ddbc9b1aeb64f5783a9e07a286de42191b7204d67b7496ddf35/Jinja2-2.11.3-py2.py3-none-any.whl
Collecting importlib_resources>=5.1 (from hvcc==0.5.0)
  Could not find a version that satisfies the requirement importlib_resources>=5.1 (from hvcc==0.5.0) (from versions: 0.1.0, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 1.0, 1.0.1, 1.0.2, 1.1.0, 1.2.0, 1.3.0, 1.3.1, 1.4.0, 1.5.0, 2.0.0, 2.0.1, 3.0.0, 3.1.0, 3.1.1, 3.2.0, 3.2.1)
No matching distribution found for importlib_resources>=5.1 (from hvcc==0.5.0)

Problem is: I can't find any importlib_resources>=5.1
Any idea, what's happening?

Is the board connected to the internet? How did you install python 3 and what version of it have you got? Should you be using pip3 (sorry I am not familiar with python packaging)?

I think if you are on a v0.3.x Bela image (which has an old version of Debian), you may struggle to find recent packages. You could consider moving to this one. The reason it is marked as "alpha" is because the newer compiler it ships with tend to be slower at building than the ones on the v0.3 images and most users wouldn't find benefits in the newer Debian (Bullseye) it ships with. But if you do, feel free to go ahead and use it.

For my purposes, I install hvcc on my host computer and run it locally and then pass the generated files to the board where they get compiled. All of this, through a simple script build_pd_hvcc.sh which is on the latest dev branch of the Bela repo. This is what I think is explained here.

Yes, the board is connected. I could install Python 3.7 et.al.
If installing was heavy on the Bela board was a misunderstanding, then I'm OK with that. I could install it on my PC and it works. I'm not clear though, where the Bela specific stuff comes in. It generates a lot of files.