The thing with the Fediverse is that things like this aren't really possible. The creators of Lemmy are pretty anti-capitalist, so the source-code won't ever support ads.
An instance admin could try to modify it to incude Ad Sense, but the users would just reject that instance and move to a free one.
I personally wouldn't mind premium features, like animated emotes and stuff for people that pay for monthly subscriptions, but again, things like that don't work in the fediverse because they won't be supported on every instance.
Maybe there will be some creative solutions that get made, but it's highly unlikely due to how things are setup.