Last time I was starting vanishing of Ethan Carter, but even though it was playable, the experience wasn't free of stutters, whereas windows ran flawlessly.
In any case, it is always nice to jump back and check out how far Linux has come.
I'm of course ignoring the fact that a lot of Linux distros still do not have Secure Boot enabled by default, and therefore do not enforce any kernel driver signing policy.
Everyone can load their own signing keys into firmware. However, if you want something that "just works", Microsoft signs a package called Shim[1] that can be loaded on most computers due to the pre-loaded keys.
A relationship with Microsoft is not needed in any way or form to have Secure Boot.
UEFI with Secure Boot enabled will only load the stage 1 bootloader if it is signed with the firmware trusted certificate. We don't know if this component is malicious, we just know it is signed by the certificate.
The stage 1 bootloader (shim) will then be responsible for loading the next component (stage 2 bootloader). It will only boot the component if it is signed with a trusted (chosen by the user/distro) certificate.
The bad guys can't insert themselves into this process, as they either have to be trusted by the UEFI firmware (protected by an owner password), signed by Microsoft (to replace the shim) or be signed by the distro's certificate.
As long as the chain is unbroken it is secure.