the last card i ordered wound up having a hybrid bios, where the vbios determined which one to load. following the instructions on this site, i was able to flash the bios and mark the legacy bios as the last one available … changing a byte from 00 to 80 and the correcting for the checksum. that didn’t work and after some research, i found out that many motherboards aren’t compatible with hybrid bioses. in short, they didn’t exist when the motherboard was made, so the motherboard doesn’t know what to do with it.
i discovered there are some gfx cards that have a manual switch that allows for one to switch from legacy/uefi, but can’t find any documentation anywhere.
prior to ordering the card, which was a rx 460, i did find a site that said it was compatible w/ my motherboard, yet apparently this brand (HP) wasn’t. i managed to brick that card.
so with all that said, i imagine any gfx card that would fit into a pci 2.0+ slot that has the manual switch would work yet i need some confirmation on the brand, as it appears many of these OEM versions vary.
the motherboard i’m using is a old m3a78-cm. from the specifications, the idea of getting a rx 460 model (2/4 GB) is acceptable, it just needs to have the manual switch.
reading another page in which one was also seeking such info, a responder commented querying the seller of such a item usually yields of no response or just saying it’s not compatible w/o knowing so or not.
if it’s of any use, this is the site that said the rx 460 was compatible w/ my MB. i think i will send them a question on what manufacturer, as perhaps they may be more compliant as their site did say it was compatible.
https://www.pc-specs.com/mobo/Asus/Asus_…Compatible_GPUs
@darool - It’s mainly “Some” Older boards, not Many boards 
I’ve never seen or heard of what you mention, with a manual switch for legacy/vBIOS, but many graphics cards have vBIOS switch for standard/OC BIOS (or other, such as compute(bitcoin)/standard, or Quiet/OC etc)
If you have one of those cards with vBIOS switch, then you could certainly set it up yourself to be legacy/UEFI or legacy/Both (UEFI/Legacy ie normal-modern)
Nvidia is tricky, some vBIOS you can’t edit, and that is what6 you need to look for in Google before you order… Can you flash mod vBIOS on the Nvidia card model or card series/family, or is it encrypted or signature checked.
AMD you do not have to worry about this with most
I suggest you go with something from AMD, if you are stuck on Nvidia then you need to check in google with whatever model/chipset family you are considering and see if flashing or modifying vBIOS is possible and allowed for that type of card.
And, once whatever arrives, if you need help, I can remove the UEFI GOP module of the vBIOS for you