I’ve got a difficult one... (I joined the forum simply to ask this question so I’m hoping you all can help me!)
I have a 2017 5k iMac 580 8gb 3.8 i5 with 2Tb Fusion Drive that I upgraded.
I put in a 4Tb Samsung 870 SSD, a 2Tb Samsung nvme and a 4.2ghz i7
After installation, everything worked...