I have been waiting for option 66 and option 67 for a while to test in my homelab pxe boot. I am not 100% certain if the issue is on my end of the configuration given PXE boot is new to me. Maybe...

@AffectedArc07 I've notice the latest version of ER605 V2_2.1.1 Official Firmware items 23. Add support for DHCP Option field which seems to implement a lot of feature required for PXE Boot server...