If you need ECC UDIMM support and true ITX, there are quite literally zero options on the market.
If you can use a "deep-ITX" board, ASRock Rack offers the only model available:
Dual X550 10GbE: https://www.asrockrack.com/general/productdetail.asp?Model=W680D4ID-2T/G5/X550#Specifications
https://www.newegg.com/p/N82E16813140115
Dual X710 10GbE: https://www.asrockrack.com/general/productdetail.asp?Model=W680D4ID-2T#Specifications
If you don't mind using ECC SO-DIMMs, there are a few ITX spec boards: