Currently RHEL 7 is better, but due to the old kernel version the compatibility between RHEL 7 and some new hardwares could become a problem. Since RHEL 7 will EOL in 2024, the adoption of RHEL 8 on newly deployed computing platforms is just a matter of time. Btw Cadence claims that the RHEL 8 is supported. Im not sure why it needs some manual tweaks to bring ICADVM201 up.