The standard v3 fields endpoint (rest/api/3/field) doesn’t seem to actually relate the the fields created in next gen projects, as far as I can tell. It’s almost like there is a classic project behind the scenes, but some of the next gen data is bolted alongside — unless I’m mistaken.
I also cannot find a way to add one of the specific field types outlined here: Available custom fields for team-managed projects | Jira Software Cloud | Atlassian Support.
