I have concerns to offer about the idea that Doppellottie is a regular human entity, as follows:

– since the smoochy gull selfie is clearly meant to communicate “I know your weaknesses but I do not share them”, Doppellottie is aware of Regular Lottie’s seagull aversion, which would be known by relatively few people

– Doppellottie knew they were going to the Slag Pit on Halloween night and there weren’t many opportunities for anyone to overhear these plans

The best flesh-and-blood suspects from this world would be associated with the outlaw wrestlepeople (specifically the Dowager’s hipster nephew), but that all happened after the Primary Inciting Incident of Miyamoto’s murder, so the temporal pieces do not fit by my (hopefully accurate) reckoning.

I have no answers to offer…