According to Lenovo, the motherboard is the RPL-HX HM770. RPL stands for Raptor Lake, HX (presumably) for the compatible / used processor.
I couldn't find out any further information (motherboard manufacturer, PCIe connections, form factor etc.) even after a thorough search - the best reference is provided by Intel itself:
https://www.intel.com/content... Note that the processor installed in this device is actually a relatively energy-saving processor built for laptops and uses a mobile socket accordingly. This is not necessarily a bad thing, but can possibly lead to difficulties if you want to upgrade individual components without replacing the entire PC.