I don't think I can install an MSI Gaming BIOS to an MSI Lightning card--I'll look into it. I know the MSI Lightning PCB was custom made, non-reference. I will look into it.

Some brands did not extend this support. This thread only lists UEFI support for MSI Gaming R9 290X, not for the Lightning version:
MSI Radeon R9 290(X) gaming/lightning card club | TechPowerUp...

Yes, unfortunately neither MSI nor PNY have a UEFI vBIOS for my cards--I received both replies today. So I just have to wait until I am able to get a more modern GPU at less than astronomical prices.

MSI Lightning R9 290X at the moment or PNY GTX 660 Ti.
My motherboard is listed in the first post, it's an ASRock Z590 series (Steel Legend).

Thanks everyone--I guess it's my graphics card that's at fault. No UEFI-compatible vBIOS, and I've just received a response from its manufacturer tech support. They said there's no vBIOS version...

Yes, isn't that the only way? When saving and exiting the BIOS, the computer ends up auto-restarting. I hear the PSU click, lights turn off, then the system reboots past the BIOS into Windows. I...

Thank you for replying!
Yes, both disks are listed as GPT.

I now think perhaps the problem is my graphics card. It does not have a UEFI-compatible vBIOS. I'm trying to see if I can get one. ...

I have just finished installing everything on my new system and realized that I can't enable Ultrafast Boot in the BIOS. Every time I enable it, it reverts to disabled.

I'm using an NVM.e m.2 SSD...