If 3.14.2 failed for you, it likely wasn’t really a Python-version incompatibility, but either you were installing a different Frappe checkout whose metadata had <3.14, or pip/build cache / env state.
Your first post stated that the installation wanted SMALLER than 3.14 so downgrading to 3.14 should not have made any difference
Your “3.14.0 worked” is probably a side effect of resetting state