It kind of feels like the most reliable predictor for "does someone intend to eventually monetize this donation-based thing" is the amount and scale of donations that they are asking for, with an exception for projects with a very large scope

More specifically, the 'red flag' to me is when a project is asking for an amount of donations that's so large, that it's obvious they haven't really tried to reduce operational costs, and instead went for the nearest most convenient or familiar option, usually one that's explicitly designed for corporate use. Think stuff like building everything around AWS.

Even if they don't *intend* to monetize things later (but it's likely that they're not very opposed to it, because it often signals a corporate background), with that kind of operational cost, they will eventually *have* to monetize things simply because the operational cost is not sustainable.