The Fediverse needs to get a handle on advertising and revenue, and what's considered acceptable and not acceptable. It's easier to do this now than after a bunch of bad actors have shown up and ruined things. My initial idea: a standard API that provides the contract between the service and its users. It would include things such as how, where and when advertising is used in that instance, whether you can opt-out, and how to do so, operating costs, revenue sources and relative amounts, etc. This API could be leveraged to aggregate lists of instances that end users could then sort and filter to find those that meet with their individual values. It could also become part of the standard UI so that users could easily locate where to support the operator of various instances, instead of relying on posting messages and hoping somebody knows where to donate (and that they are providing the true information).
Yes, I do realize there's a bit of a "herding cats" aspect to this. And there are those who are just completely opposed to any sort of "monetization" at all, but to me that's just an argument in favour of making it as transparent and discoverable as possible.