"This was denylisted" works perfectly fine. It's no different grammatically from "This was blacklisted;" the only difference is you aren't used to it yet.

Denylist contains the verb you are looking for, the phrase would be, "This was denied."

That's the point of the change -- it's clearer about what happened.

It's just not recommended. And it's just because saying what adding something to the list does is more precise than saying black list or deny list.

It's only not recommended (not "don't use"), so presumably can be used if it's the clearest way to describe something:

> Not recommended: To denylist an IP address, add it to the dos.yaml file.