ERROR: wxGUI requires wxPython

Q: I'm trying to start the graphical user interface but it tells me

ERROR: wxGUI requires wxPython. No module named 'wx'

A: The solution depends on the operating system in use. In general, the package "python3-wxPython" (naming may vary) is needed.

Things to verify:

• do you use Anaconda? Please check if you have colliding Python versions. If not, read on below.

Linux specific notes:

• Fedora:
  • sudo dnf install python3-wxpython4 (or via software manager)
• openSuSe: python3-wxPython, see discussion in https://forums.opensuse.org/showthread.php/542338-grass-7-8-from-the-science-package (and elsewhere - TODO: any better solution?)
• Ubuntu:
  • sudo apt-get install python3-wxgtk4.0 (or via software manager)

Conda related notes (note that many user actually do not use conda):

• Here a suggested solution with a virtual environment: https://stackoverflow.com/a/58902163/452464