Most Mastodon, Friendica, Calckey instances accept donations.
It is likely that kbin/Lemmy instances will likely follow the same model.
Advertising would not work on the Fediverse as the adverts would be blocked by other instances so the spread would be very limited so not attractive commercially.
That is one of the beauties of the federated model.
Also, as there is no algorithm or data about user interests there's no scope for advert targeting which advertisers would want.
The whole ethos of the #Fediverse is anti commercial.