interesting, thank you for the advice.
Then I need to re-consider the list of MBs. What I found so far is this Supermicro list based on customer support reply Bifurcation on Supermicro X12STH and Supermicro X12STL boards -- short answer: No
according to ASRock Rack E3C246D4U - The Perfect Media Server Motherboard? E3C246D4U supports bifurcation, could not find anything specific E3C246D4U2-2T, but in comments someone mentions this board with “4 x NVMe”, so I presume it should support bifurcation.