Onboard graphics with Z370 Fatal1ty Pro Gaming i7

New PC:
Asrock Z370 Fatal1ty Professional Gaming i7
Corsair Dominator Platinum 4x16GB
Intel i7-8700k

At first I got only to boot code A2 during boot a bunch of times, regardless of having my SATA SSD connected to various ports or not at all. Tried reseating RAM, one stick at a time, resetting CMOS etc. After trying them all in different slots, I slot in my nVidia GTX 970, and now it boots.

With the discrete GPU I can access UEFI and I enable concurrent iGPU. From Windows 10, the Intel graphics works once I install the drivers.

After removing the GTX 970, however, I'm still not able to get any display output for UEFI from internal graphics (I've also tried this without having enabled the concurrent iGPU setting), or see anything before the OS loads it's drivers. Only after Windows loads do I get any output.

UEFI is 1.10 out of the box, which is the most recent non-beta release.

Smells like a UEFI issue. Is this forum the correct place to report this?

Oh I see, it may be related to using a TV. Yes, I was hooked up to my Sony TV via a Yamaha receiver, both around 7-8 years old, as they were most conveniently available where I was testing the system. Since my post I've found people mention Intel integrated graphics and some poor HDCP implementation.

Works fine with the nVidia graphics.

Fast boot is disabled by default from what I can see, and I haven't changed it.

Intel seem to put all responsibility on the motherboard vendor for these issues.

Is this something Asrock has fixed in the past, or will I just have to live with it?