Computer won't boot with newer CPU after bios update, but will with older

Hi all

Hardware

Asus b550m-k / msi b550m pro

Ryzen 5 5600gt /ryzen 5 1600

64gb ram

3080

Issue

My pc will post, but then either freezes on the mobo logo spinning wheel, or gets caught in a loop resetting.

Background

I recently went to update my bios (I don't what what version it was on previously) which seemingly went fine. But then the issue of it freezing or getting stuck started.

Saw

I've tried everything I can think of: using one stick of ram, disabling safe boot, disabling xmp, setting default settings in the mobo, flashing to a previous bios, changing harddrives, trying to boot to a recovery usb, disconnecting everything unnecessary, and nothing will work, exact same issue.

I've then tried same hardware except on the msi board, exactly same issue, same freeze spot.

After that, I put in an old ryzen 1600, and it boots into windows without issue.

My questions to anyone who can help are

Is my 5600gt fucked, it's relatively new and worked fine. How can I test it, and is there anything else people can suggest to try?