Looks like the Link check step in the CI is broken. It has always been allowed to fail for a long time.
Would be great to fix them all.

Please see the output here:
https://github.com/python/devguide/runs/2463428458?check_suite_focus=true

While looking at the output, I noticed that pypy.org is listed as broken. I think that's the correct url though. I've filed the issue here:

pypy/pypy.org#23
Update: the url seems to work now.

But it would be good to look through the rest and update the urls accordingly.