Integrating HIBP checks in online platforms is nice, but what about the public (and admins) at large? Has HIBP been integrated in upstream for registration/login forms in "usual" software? I'm thinking about Nextcloud[0], Wordpress, GitLab, etc.

There should be no harm in doing it, and the admin would get a new switch "check the password with HIBP at login time (Y/n)". This could have a good impact - and it could be done from either client or server-side.

EDIT: after checking, it's already in Nextcloud: [0] https://github.com/nextcloud/password_policy/commit/fed9c37f...