Hi, I think we have a discussion for the same issue on this post. I ran through a roughly two months process with Framework support for diagnostic, leading to a mainboard replacement.
The point is that it could be barely anything before the mainboard - so you have to test everything to come to the conclusion of a faulty mainboard.
To help, I gave a summary of the steps I went through here.
Hopping this could help you find faster what you have, and eventually shorter the support processes.