3.10 is not supported by Netlify at this moment, even using the above various ways to set a version:
10:14:06 PM: Starting to install dependencies
10:14:06 PM: /opt/build-bin/run-build-functions.sh: line 328: /opt/buildhome/python3.10/bin/activate: No such file or directory
10:14:06 PM: Error setting python version from runtime.txt
10:14:06 PM: Please see https://github.com/netlify/build-image/blob/focal/included_software.md for current versions
10:14:06 PM: Build was terminated: dependency_installation script returned non-zero exit code: 1
10:14:06 PM: Failing build: Failed to install dependencies