Workarounds if I can only boot using CSM?

From the OpenCore guide, we are advised to disable CSM.

I'm using a HD 7790 which isn't UEFI compatible so the bios is forced to boot in CSM mode. Is there a workaround for this? I get a black screen and cannot see the installer/ disk utility.

I tried removing my GPU, then enabling UEFI mode and displaying using igpu. I was able to install big sur this way. Then I inserted back my GPU after installing BigSur and I can get video out from my displayport, but my DVI ports are not working if I do it this way.