No, I’m not saying that – it’s just one possibility among many, but I don’t have any specific knowledge about what the Nuendo/Cubase code is doing. The fact that ProRes doesn’t work either suggests there is probably something else going on.
When you tried the 1050, did you also disable the onboard Intel graphics, either in the BIOS/UEFI or in Windows (Device Manager)? If the system can still see both GPUs some software will still try to use the integrated GPU for things. I’m on a relatively modern AMD CPU which has integrated graphics, and although I have an RTX 3080 in the machine that I use exclusively, I have to specifically disable the AMD graphics or else Steam (for instance) does strange things and certain games will freak out or even crash.