it kinda is. Or put it another way - we're into the 4th decade of mainstream OSS success, and it's _still_ necessary to ask this question. That might give some clues that it's a difficult question with no current solution.

As you noted most of the common suggestions are either slimy, unsustainable, or simply don't work.

So I think you need to be clear on your objectives. Is it making OSS? It it making money? You can focus on one and then get maybe some of the other, but getting both appears (at least historically) to be both hard and rare.

For example selling software as "source supplied" is not OSS, but will likely improve your income stream. Or you can make pure OSS stuff, and get minor amounts of money via donations, support, whatever.

Both approaches are valid - you just need to decide which road you want to take these projects down. (And obviously you can split your projects between different approaches.)