add more maintenance notes

Author: Oliver Schoenborn

README.rst

@@ -433,6 +433,17 @@ Maintenance
 - Increase the package version in setup.cfg and setup.py
 - Add a python version if latest python is not in `tox.ini`
 
+Notes for Ubuntu:
+- My experience today installing python 3.5 to 3.11 on Ubuntu 18 was surprisingly not smooth. I had to use these
+  commands:
+  - sudo apt install python3.5 (ok)
+  - sudo apt install python3.x-distutils for x=9,10,11
+  - had to use `python -m pip` intead of just `pip` otherwise wrong version would get found
+  - used `sudo update-alternatives --install /usr/bin/python python /usr/bin/python3.x 1` for all x
+  - used `sudo update-alternatives --config python` to choose which python active
+  - had to install setuptools from git repo otherwise weird pip error (used https://stackoverflow.com/a/69573368/869951)
+  - note however that once the correct tox installed,
+
 
 Acknowledgements
 ----------------