> If anyone else is in this situation of desiring to sunset a social platform

I feel like once you arrive at the situation where you want to free up your time and shut down a project (Which is already a hard decision to arrive at) you'll not want to put in extra work to run some contest, pick a winner, hand over domains, infra or figure out a way forward.

It already takes me a lot of energy to shut down side projects with little to no users instead of just keep paying for it.

Fair enough. Maybe the threshold for doing as I suggest should be if you are just starting to lose enthusiasm.