I'm a bit late to the game, but I don't understand what this fuss is all about, from a technical point of view. I just created a git repo this morning and the default branch was named "master" (using the git command line). Then I pushed it to github to make it visible, as I have done several times before. The command line instructions at the "new repository" interface on github suggest changing the branch name to main, but I did not do that (just for trying) and now I have a brand new github repository whose branch is named "master". Basically github allows to name your branches however you like. The example instructions suggest that you rename your master branch to "main", by running this code on your command line:
git branch -M main
But that is all. You can name it "trunk" if you want, for all that matter.
Now, I think that the whole github renaming thing is a bit ridiculous and probably a faux pas on their part. But the people complaining about "the great rename" sound even more ridiculous: as far as I can see, there's no rename, just a stupid modification of the initialization instructions that suggest that users rename their branch. All that fuss for the damn "git branch -M" line?