Update Python version

First, install the add-apt-repository:

sudo apt-get update && sudo apt install software-properties-common && sudo apt update

Then, adding deadsnakes and updating

sudo add-apt-repository ppa:deadsnakes/ppa && sudo apt-get update

Verify package list

apt list | grep python3.10

Installing latest Python

sudo apt-get install python3.10

Adding Python versions to the list of alternatives

sudo update-alternatives --install /usr/bin/python3 python3 /usr/bin/python3.8 1
sudo update-alternatives --install /usr/bin/python3 python3 /usr/bin/python3.10 2

Configuring Python3 (Select the correct number, not Auto)

sudo update-alternatives --config python3

Finally testing version with python3 -V

Python3.9

sudo apt update && apt list | grep python3.9 && sudo apt-get install python3.9 && sudo update-alternatives --install /usr/bin/python3 python3 /usr/bin/python3.9 3 && sudo update-alternatives --config python3

Select Python 3.9, then python3 -V