Hi Onalp,
The short answer is no, we haven't tested anything beyond 4k2k 60Hz. From the specifications perspective I believe The Vanity
PRO won't work with FRL or anything beyond 4k, simply because it is "only" HDMI2.0b compliant. Although the HDMI subsystem is software upgradeable, FRL support requires changes in hardware due to different signaling schemes.
Best Regards,
Pavel