While the GPUs not on the supported list will probably not correctly be identified in the CIMC's inventory, I think your biggest issue will be making sure you have the right PCI-riser kit present, and probably the GPU power cable kit ((UCSC-GPUCBL-240M4)).
Use riser 1 version 1A (slot 2) or riser 2 (slot 5) for GPU cards. These are PCIe 3.0 slots...
Expect the CIMC's thermal calculations/fan control to run in jet engine mode, as it won't have a built in profile for the unsupported card.
I would thoroughly review the GPU section below to make sure you have the right riser and GPU power cables to connect.
https://www.cisco.com/c/en/us/td/docs/unified_computing/ucs/c/hw/C240M4/install/C240M4/gpu.html#14039
Good Luck,
Kirk...