11.7.3 Joining Inaccessible Nodes After Forcing an Upgrade
You can add inaccessible nodes to the cluster after a forced cluster upgrade.
Starting with Oracle Grid Infrastructure 12c release 1 (12.1), after you complete a force cluster upgrade command, you can join inaccessible nodes to the cluster as an alternative to deleting the nodes, which was required in earlier releases.
To use this option, you must already have Oracle Grid Infrastructure 19c software installed on the nodes.