I have recently setup a 64bit Batocera system on my PC.
I have set this up almost exactly the same as my Odroid and Raspberry Pi 3 (which load Dreamcast fine).
When I try to run a Dreamcast game on my 64bit machine, the game goes to loads, the screen goes black and I am back at the Dreamcast screen.
I have all the correct BIOS files loaded into the BIOS folder, so I don't think this is the issue.
I have not upgraded the onboard video yet, so I don't know if this is a related issue (I have a PCI-Express card coming soon).
Note that all other primary systems work fine (Nintendo, Sega)