It probably goes against the philosophy or whatever of FOSS or Lemmy itself, but why not be a little evil so that you can actually sustain yourself? Donations can bring us far, but small non-intrusive ads can be a bliss in the skies for the people actually hosting the instance. Especially if there are millions of users uploading thousands of images and videos. This is extremely expensive.
Is running ads really that taboo?
EDIT: some people seem not to get the point of “millions of users”, which presumably includes non-techies that do not use adblockers. I mean that without ads (or mining?), no instance would be able to scale to the point where it can compete with Reddit for example. If you were to want that. And not for profit, but solely for sustainability.
The point of the fediverse is that hosts can pick their own business model - free, freemium, ad-supported, subscription. Just like e-mail, you sign up with the provider who provides the type of service you think best meets your needs. If they piss you off, you move to a different provider.
If the fediverse demands hosting for millions of users, someone will make a server to host millions.
I personally think “big” instances should focus on user/identity management, while communities live in small groups on small instances. This lets the identity providers include/exclude with much better granularity (compared to the beehaw mess) making the communities much less susceptible to being collateral damage.