Raised here - https://github.com/rancher/rancher/issues/47274

All fixed - was a case of RTFD, the upgrade to 2.9 required TLS validation unless otherwise specified, in our case our network is isolated and private and uses self signed certs.

Spoke too soon... when trying to interact with our cluster - adding nodes things went wrong, so tried to restore from the backup to the older version, now stuck in a loop...