I am pretty sure TianoCore is also used by AMD systems as a reference as well.
Here's a similar situation that happened in 2019 at Lenovo's site
https://support.lenovo.com/cl/es/solutions/LEN-22660
AMD systems are listed as well.
As for most board vendors nowadays, I think they barely do anything with the code itself and just create the setup utility and boot logos. It is highly likely that they're affected too.
Hey Shadow, what do you think of this guy's cock?