I have installed python3.8 and have found no reference on how to get pip3 to talk to it on ubuntu. On macos I had explicitly installed pip3.8 and that has been crucial to getting all packages lined up correctly.
pip3 was installed as follows based on numerous recommendations:
sudo apt-get install python3-pip
But it is pointing to python3.6:
$ pip3 -V
pip 9.0.1 from /usr/lib/python3/dist-packages (python 3.6)
Please do not suggest anaconda or venv: there are reasons we are using directly installed python3.8.