This is going to have to be a per-instance thing. Smaller instances may be fine indefinitely with no donations/outside funding, but large instances will eventually require dedicated hardware or kubernetes clusters to scale adequately. Larger instances absolutely should run funding drives as they need to in order to keep up with their expenses. That, or we get ads on here eventually... which would suck.

Another option would be to do federation-wide fundraising and split it out with crypto or something to instance owners that opt in... take some arbitrary cut for the Lemmy devs and split the rest out to participating instances based on their share of active users or something. But that would need some serious anti-fraud controls to keep a rogue instance owner from creating a ton of local spam accounts to rake in funds.