After some searching on the old and new websites, I think I've found it. I don't think we've had get.xml in quite some time, but we have instructions on accessing the TEI locally on this page: https://tei-c.org/guidelines/p5/

I'll just go and add that now!

No--I won't be adding that. It makes sense because it's the one place where we mention setting up a local environment for working with the TEI Guidelines, so I think that is why @rettinghaus and I both reached for that link. But we want something that comments on the local setup environment for Stylesheets and Guidelines...I wonder if this is in the Vault, or whether it's time to write a new version.

Aha! I think it's TCW 32 that we need, yes? https://tei-c.org/documentation/tcw32/

But TCW 32 also has a dead link to the mysterious get.xml, referring to it as a whole repo on "Using the TEI Guidelines": see https://github.com/TEIC/Documentation/blob/b9e7e139957339fc1cc06c5a48565cfaa6e65615/TCW/tcw32.xml#L105

The document is still available under https://old.tei-c.org/guidelines/p5/using-the-tei-github-repository/. I think this is more how to (simply) set up everything locally.

So is https://tei-c.org/documentation/tcw32/.

If you need to know how to clone a repo or something else, there is plenty information on GitHub itself.

I think the best replacement for now is still the overview: https://tei-c.org/guidelines/p5/.