TB4, USB4 And USB-C all use the same connector. Same how Mini Displayport is also used as TB2 port. So it more on the protocol than the connector.
So EGPU would be possible but would not all fit in an expansion card. But would be interesting as a card. But would have to be more than 1 slot or external wire so a docking card for the eGPU and/or External dock.
The CPU is Thunderbolt 4 certified, but not sure if it has been enabled on the motherboard. From the YT videos creators have made (Adam Savage Tested, LTT, and more) have confirmed USB-C spec but from what they have shown it does not show that the USB-C Expansion card is TB4 or USB4 speeds. And would need more testing with a Thunderbolt dock or eGPU to the internal port to test
It would be likely that the connection to the chassis is TB4 but the expansion card might be the limiting factor as @The_Cyber_System has also said.