OptiPlex 780 should be able to boot with CLOVER.  Just make sure to create the boot disk (USB) properly.  Instructions to create NVMe boot in legacy BIOS  can be reviewed here. For BIOS modification method, instruction for OptiPlex 790 and 990 is also available.
Hi there, I have a Dell Optiplex 780, with only legacy boot and without support for UEFI boot and therefore apparently not NVMe boot either , the main boot Windows 10 SSD drive is MBR obviously, there is a chance to modify the BIOS legacy to somehow boot from NVMe or boot from NVMe using Clover like this video [URL]  ?, thank you
Is there a chance to boot from NVMe with the Optiplex 780 mT?