Restoring Horizon DaaS platform appliances to previous versions after upgrading to the 21.1.0/9.1.0 release is supported.

To ensure that the platform setup can support anticipated/unexpected restores of any appliances of version 20.2.0/9.0.0/9.0.1, before performing the Restore you must copy the entire directory (/opt/vmware/horizon/link/transfer/ from the 20.2.0/9.0.0/9.0.1 Horizon Air Link appliance to the new 21.1.0/9.1.0 Horizon Air Link appliance at the same path (/opt/vmware/horizon/link/transfer/). This can be done at any point in time after installing the 21.1.0/9.1.0 Horizon Air Link appliance, including after upgrading the platform Management appliances (SPs and RMs).