It is perfectly possible to use a PCIE 4.0 card (e.g. RTX 3080) on a PCIE 3.0 motherboard (e.g. all Z490 chipset motherboards). It should also be possible to use this bracket with a PCIE 4.0 graphics card, the riser being just an "extension" of the PCIE.

Here is the answer from our supplier: "They are compatible, but you may have to select it in the 3.0 motherboard bios".

Following this answer, I found information that in general, it is possible to insert a PCIe 4.0 card, but that for this to work without problems, the communication with this card must be downgraded to PCIe 3.0, even if the motherboard supports PCIe 4.0.

The source of the problem with PCIe 4.0 is that it can only handle PCB traces up to 7 inches before needing a redriver/retimer, so to make this product work at full PCIe 4.0 specification, it would probably need some changes to the cables/rectifier itself, so probably a new revision of the product will be announced by the manufacturer or information will be added to the product accordingly if the manufacturer tests it and finds it compatible with PCIe 4.0.

This longer version of the answer was made after talking to Phanteks technical support staff.

So, for now, the final answer for this product is :
- Support for PCI Express standards: 1.x, 2.x, 3.0,