Your motherboard fully supports the Samsung NVMe 970 EVO Plus.
Your motherboard fully supports the Samsung NVMe 970 EVO Plus.
The term "Not supported" indicates that the Gigabyte Z170x Gaming 5 EU is not compatible with the specific component or feature shown in the image you referenced. It means the part won't work as intended with that particular setup.
It seems the SATA connections overlap with PCIe channels in the M.2 slots, which can cause some ports to stop working when you insert an M.2 device. The 970 Pro supports a four-lane M.2 slot, meaning it won’t interfere with the M2H port if used correctly. (Inserting into the M2D slot will disable ports 0, 1, 2, and 3.)
the ssd uses pci-e x4 interface. There are two sets of tables, one for each m.2 port. Each port supports three SSD types: sata, nvme pci-e x2 and nvme pci-e x4. In the middle section of the tables you'll find which ports are affected by the SSD type. For example, if you place the x4 ssd in the M2D_32G slot, certain ports like SATA3_0 through SATA3_3 stop working. You'll only have SATA3_4 and SATA3_5 operational. On the other side, M2H_32G has no disabled sata ports and all indicators are green. The second row mentions sata express which isn't relevant here.