Is there a way to see all the branches that are archived? I used this answer to archive some of my branches. and there's a way to restore the branch after I have archived it, but only if I know the name. If I don't know the name, is there a way to see all branch names that have been archived?
some sort of
git branch -archive
Per the answer you linked, the "archive" operation is made by creating tags on each branch to be archived and then removing such a branches. So, after all you have no branches, you have only tags.
To list all tags with archive prefix in the name you can use
git tag -l "archive/*"
(note the archive part of command - it should match with a word you used when creating archive tags.
So, finally, to restore some archived branch from a tag (for example, named archive/test123) you can use
git checkout -b test123 archive/test123
