Lakka has reicast but its slowSince it's the second time you (or someone else) asked this here without getting an answer:
The libretro core for the Dreamcast is called Reicast and as far as I know it's not available for the Switch yet. It would be surprising if it would be as the Dreamcast is even newer than a N64 which doesn't run well yet as we're still waiting for someone to take on that dynarec bounty.