Because you want to work with the ros noetic software, I think the best route is to set up an environment for it in Ubuntu 20.04.
Anaconda is a great way to create multiple software environments that require different packages and setups to make them work.
You can get started by downloading Anaconda (Individual Edition)
https://www.anaconda.com/products/individual
It can be a lengthy download, so allow some time for it to work.
When you get your command prompt again, please run this:
conda create --name ros python=3.8 anaconda
This sets aside an environment named ros that has python 3.8 as your base. It will also download and install a number of compatible tools that work well with python 3.8
To use this environment, you will need to activate it.
conda activate ros
Once you start working in this new environment, your terminal command line will be updated to show (ros) in the prompt.
Anaconda supports the Ros Noetic Desktop Full installation
https://anaconda.org/robostack/ros-noetic-desktop-full
and Ros Noetic Rosbag
https://anaconda.org/robostack/ros-noetic-rosbag
Each page gives you the command to run in your ros environment.
The beauty of this is you don't have to settle for one version of python on your system. You only really need it when you're trying to do robot os work. You can even open up another terminal and simultaneously do work in your default (non-conda environment) or activate several conda ros environments on your project.
I have several software projects (MongoDB, Superset, Flask web development) that have conflicting or overlapping needs. I make a conda environment for each one and never have to troubleshoot issues related to my software environment.
