please see this question: How to default Python3.8 on my Mac using Homebrew?
I'm trying to accomplish the same thing. I brew installed python and that gave me the latest 3.9; however, I would like to use 3.8 to maintain dependencies.
When i check terminal for the version of python the result is always the macOS default of 2.7.
I've used this method above and many other methods, but I am new to homebrew and zsh and I have not found a work around.