Hi Cameron,
Which version of Tianocore did you use? Did you make any changes to Tianocore to get it to work (because it still doesn't work for me)? E.g. did you have to change debug console port settings (similar to those needed for SeaBIOS to use MMIO serial)?
Did you specify the GOP driver in coreboot, and if so, which file did you use? Or did you include the GOP driver in the Tianocore build?
Would you by any chance be willing to share the coreboot and Tianocore config files for your working combination?
Regards,
Tahnia