Unable to access server locally with privacy badger extension

It’s not a bug. Your local DNS resolver is blocking the private domain plex.direct

If you add the exception to allow

rebind-domain-ok=/plex.direct/

Pfsense uses:

server:
private-domain: "plex.direct"

or other similar syntax.

Some DNS resolvers do not have this ability. You will need turn off DNS rebinding protection.