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.
I use https://1984.hosting (for privacy) to run my instance on a VPS. I’m using 1 core 2GB RAM VPS and that costs 10 dollars a month. So far everything looks to be running pretty well.
There probably are cheaper VPS providers as well, so you likely will be able to go cheaper.
And how many users can that host? With that price there maybe not really a need to actually run ads. What work is involved with running an instance?