This makes me 😭
UPDATE: Thanks @nekusoul@lemmy.nekusoul.de for this update: The issue has now been commented on and was closed by the maintainer, where they explained why those blocks would be nonsense. But it appears the OP wants to still talk with maintainer privately about it.
I bought the domain, set required domain records as per protonmail docs, waited for verification to complete and enabled catch-all thingy.
https://proton.me/support/custom-domain