• Used Detours library instead of MinHook as the former supports ARM64.
• Registered COM in DllMain() instead of initquit() since the foobar2000 component services initialize in unpredictable order. Made this change because I was seeing the script from another component trying to get the ActiveX object before it was registered by my component's initquit().
• There is a double reference count in the Factory constructor with its AddRef() causing some unfreed memory left over on exit. To fix initialize refCount to zero instead of one like so: MyCOMClassFactory() : refCount(0) {}

void init()
{
    // do stuff
}

FB2K_ON_INIT_STAGE(init, init_stages::before_ui_init);

Your comment about refcount and DllMain got me curious because reference count is initialized to 1 in all COM example codes everywhere, and using DllMain for such stuff is forbidden by Microsoft's documentation. Are you people certain you know what you are doing?
DllMain best practices
OleInitialize docs, which says directly "do not call OleInitialize or OleUninitialize from the DllMain function".

• If using the ATL smart pointer class, initialize to 0. This is how CComObjectRootBase is coded.
• If using a native pointer, initialize to 1 and call Release() before the function returns. This is how many examples implement/use these as Case correctly calls out. Using this second alternative has the downside of needing to release the reference if the function returns prematurely due to some failure in addition to the regular return. In this case if CoRegisterClassObject() fails; note that this function itself calls AddRef() which requires an eventual call to CoRevokeClassObject() to Release().