Currently, Site24x7 on-premise poller supports SNMP protocol to monitor the Network devices like Switches, Storage, Firewalls.
As technology is advancing day by day and network devices migrating from SNMP to REST API for monitoring.
As on Jan 20, 2023, the Site 24x7 does not support monitoring network devices via REST API except Cisco Meraki Devices. Please consider this as a feature enhancement request and try to include this in a future release.
If you want an example, Pure Storage Flash Array does not support standard OID hence unable to Poll via SNMP, however, it does support the monitoring through REST API.
Please let me know if you have any questions.