I'd be very sceptical that you'd be at fault for not paying any tax here. That is supposed to be handled by the seller. So eBay would have to take the blame for selling it in the wrong way. Just having a disclaimer down on the page simply isn't enough. At least for Swedish standards.
That looks correct according to the layout. One simple thing to do is to clear CMOS.
But then I'd look at the CPU socket pins to make sure no pins are bent. And you can clean the cpu pins (NOT the socket pins since that's far too dangerous) with some isopropyl alcohol. Also inspect the DIMM...
Its very possible that the seller didnt update the bios and it wont allow 2933 memories.
Also, whats the memory you are using? PN.
And yes, 2933 should downclock without any issue. Support for gen1 wouldnt be removed because of new bios. It has code for both variants.
This should be easy to verify without any adjustments. Just put a drive in naked without any cage around it. I have a few HP M6720 that i run without any drive cages since the JBOD was delivered without and buying the sleds are more expensive than the unit itself.
For sure these systems are really expensive to buy. But they arent really intended to buy as a private customer or the like. Its a product that was designed and made in 2014 and has a long life. When I say the value is 200$ its because its so old. The first processor in the series was made 15Q1...