I managed to downgrade to iTunes 12.4.3 (Previous version) on Mac OS X 11.10.6, in a pretty manual way, now I got my old artists list back!
For you who want to try this solution, it should work in theory on any OS X version:
1 - Download iTunes 12.4.3 here: Download iTunes 12.4.3 for OS X
2 - When you mount the downloaded .dmg file, you'll have this:
When you double click the Install iTunes, you'll have a dialog warning message saying "A newer version of iTunes is installed", then that's it.
You have to delete the new iTunes, but you can't do so by deleting it's .app folder through Finder, you'll get a message saying "You can't delete this app because it is required by OS X". So we'll do it through command line.
3 - Open a terminal (cmd+space => type terminal => hit Enter), then carefully type this command:
sudo rm -r /Applications/iTunes.app/
(You'll be prompted to enter your password, go ahead and hit Enter. This is a command line to delete a folder and its content, the sudo is essential because it enables you to run this command as root)
4 - Then install iTunes in the previously opened mounted volume, it should install correctly.
5 - If you try to open it, you'll have a dialog saying something like "The .itl library file was created using a newer version of iTunes", then you'll be stuck with "Update" or "Quit" options. Click "Quit" for now.
6 - Go back to the terminal, and carefully type this command:
sudo rm ~/Music/iTunes/iTunes\ Librar*
(Note the asterisk at the end, it is very important. This will delete the iTunes configuration files created by the newer version)
7 - Now iTunes should be opened successfully, don't be surprised if there is no music or content showing up, you'll just have to import your existing library: cmd+O => Browse to your library location, by default it should be:
Music => iTunes => iTunes Media => Music
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If you want to try this solution, please do so carefully or have a computer knowledgeable friend of yours with you while doing so.
