The 7.x simulator was a completely different architecture. The 7.x sim runs both instances of ontap as separate processes on a single linux system. It was able to simulate HA because both processes can share the same disks and both have access to the same ram so spoofing RDMA with DMA wouldn't have been a big challenge. In 8.x the simulator is based on DataONTAP-v, so each instance runs it its own VM without the layer of linux underneath. Its a much more realistic simulation but makes HA more challenging to pull off.
What that means for you, is you need to read the 7.x simulator install guide so you can build a linux VM to run it on. Its didn't ship as a standalone VM, so you have to build your own.