For an image-based backup of the SDDC Manager, use a solution compatible with the VMware vSphere Storage APIs - Data Protection (formerly known as VMware vStorage APIs for Data Protection or VADP).
vSphere Storage APIs - Data Protection compatible backup software connects to the vCenter servers in the management domain to perform the backup to a remote site. In the event of failure, the backup software connects to the vCenter servers in the management domain to restore the VMs. If the management domain is lost, the vCenter servers are no longer available and must be restored first. Choosing a backup software that supports Direct Restore to an ESXi host allows restoring the vCenter servers.
For an SDDC Manager backup, connect your backup with the management domain vCenter Server. Configure the product to take non-quiesced backups of SDDC Manager. To reduce the backup time and storage cost, use incremental backups in addition to full ones.