Computer Graphics Cards for PCI Express 2.0 x8 | eBay
If you have no M.2 SSD installed in the Gen 5 slot, then the graphics card will run with a full x16 lanes configuration, but when you install an SSD, the GPU slot will be limited to PCI-Express 4.0 x8 (with bandwidth identical to PCI-Express 3.0 x16).
Which PCIE slot in one GPU configuration - ROG Forum
On a modern system especially as a server of some sort, you can get by without any at all - You can go with onboard video (avoiding the use of a PCI-E slot for video card), ethernet (so you don't need a expansion slot for it either) and so on.
GT730 64Bit 810MHz 2GB DDR3 video card with PCI Express 2.0, DVI ...
Will this card work in a PCI Express 2.0 slot, even though its meant for a PCI Express 3. – Learn about MSI - NVIDIA GeForce RTX 2070 Super 8GB GDDR6 PCI Express 3.0 Graphics Card with 2 Answers – Best Buy.