I fixed it now ![]()
I stopped the lighttpd service & disabled that service (link - Upgrading to v6 (pihole -up) didn't disable lighttpd - #2 by smithbill ), which brought the admin console back.
I then told Pihole "plz to use Cloudflare DNS. Kthanx!" (PiHole admin console > Settings > DNS) which then brought the Internet back.