Trying to upload RHEL 8.5 to Harvester but fails. Is it to big of a file? iso is 10gb

Harvester should be able to handle it. I suggest downloading ISO locally, verify checksum to make sure it's not corrupt, then upload from local machine into Harvester (you can use "python3 -m http.server" to serve from current directory - URL will be http://local_machine_ip_address:8000/filename.iso )