My specific driver is an open source file system driver (WinFsp). This is a software only driver that requires attestation signing. There was a period a few years ago when Microsoft required WHQL testing for Windows Server (which I did), but they seem to have dropped this requirement.

The linked OSR thread has a lot of other driver developers including a lot of them maintaining drivers for hardware devices.

With Microsoft removing our access to the hardware section of the partner center, we are not able to submit drivers for either attestation or WHQL testing.