Yes, you can use streaming backups triggered on a HANA database running on SLES to restore it to an RHEL HANA system and vice versa. That is, cross OS restore is possible using streaming backups. However, you'll have to ensure that the HANA system you want to restore to, and the HANA system used for restore, are both compatible for restore according to SAP. Refer to SAP HANA Note 1642148 to see which restore types are compatible.