For some reason I can't find the wiki page that actually says this anymore . . .
RHDN-DataCrystal integration is broken, and no one has time to maintain it; independent DataCrystal account registration is disabled for all the obvious reasons. You'll have to hop on the RHDN Discord channel linked from the wiki Main Page
, be verified as a real person, then follow the pinned instructions in the #datacrystal channel to have a DataCrystal account made for you.
The suggestion by Cyneprepou4uk may work as well.