About all links on page 'help us' are broken (404)
From page http://lilypond.org/website/help-us.html only link 'bug reports' works, all the rest (issues, documentation suggestions, etc.) are broken.
Guess that is because they're prefixed with http://lilypond.org/doc/v2.23/...
, manual changing version to 2.21 there makes them work again.