Hi ,
Welcome to our new Microsoft Q&A Platform.
DHCPv6 uses a "boot URI" instead of a separate TFTP server IP address and filename. You should be able to just set this to any URI that iPXE understands.
In my lab,the bootfile URL (option 59) does not exist as a standard predefined option for DHCPv6 in Microsoft's DHCP server.
I define it via Microsoft's DHCP server UI. It allows new DHCPv6 options to be added, but these options never show up in the option list.
As I know,Linux ISC DHCP or Cisco switch have 067 option in IPv6.
Best Regards,
Candy