RHEL 8.4 is now supported by SAP for HANA v2.0 on Power Excerpt from SAP Note 2235581 – SAP HANA: Supported Operating Systems: https://launchpad.supporthttps://launchpad.support.sap.com/#/notes/2235581

Supported Operating Systems for SAP HANA 2.0 on IBM Power Servers
For running an SAP HANA 2.0 system on IBM Power servers the following operating systems are supported:
– Red Hat
– For general information how to configure Red Hat for SAP HANA, see the configuration guides attached to https://launchpad.support.sap.com/#/notes/2009879.
– RHEL 8 for SAP Solutions / RHEL 8 for SAP HANA – consult https://launchpad.support.sap.com/#/notes/2777782 for recommended OS settings and https://launchpad.support.sap.com/#/notes/2055470 for supported processor generations.
– 8.4 (HANA 2.0 SPS05 revision 55 and newer)
– 8.2 (HANA 2.0 SPS04 revision 48.02 and HANA 2.0 SPS05 revision 52 and newer)