OP already said they had tried using virtual environments and why it wasn’t working for their use case.
In my experience of helping Python users, I find it’s better not to continually insist on taking the high ground, especially when they tried it and it failed for some reason, sometimes you need to stoop down to just helping getting things working.
--break-system-packages is there for exactly the situation where the doing the “right thing” doesn’t work for the user for some reason.
The linked SO post goes though different solutions, in fact that SO post was previously discussed and edited to include solutions that did not just advise users to break their environment: The most popular advice on the internet for `error: externally-managed-environment` is to force packages to be system installed