While I have not tried it with Proxmox, I have had good luck with Starwind's V2V converter. It does not have native support for Harvester, but it can output to a QCOW file which can be uploaded to Harvester.
You still may have to fiddle with drivers, drive types, and such (i.e. load the Suse driver pack onto the VM prior to the migration), but, "in general" it should work.
Fair warning: Starwind V2V, while free, is also "nagware" (IMHO).