Question about HP Omen 40L GT21-0700nz

According to the manufacturer, they do not use commercial motherboards, but specially designed ones, and not always the same model:

We do not use commercial motherboards with our complete systems. We don't use commercial motherboards with our complete systems. The motherboards are specifically designed for the PC in question, so there is no dedicated motherboard model that we can name. If I were to give you a close model, it would be an HP Omen Z690 motherboard.