Ask HN: How do you know if there's a market/need for an OSS project?

Find something you need done, and make software that does that.

Trying to solve other people's problems which you don't share isn't likely to lead to real solutions, nor be appreciated by those you're trying to market it to: "this person has no clue what our needs are and they want us to use their solution to the problems they imagine we have"

My two-cents is that if you're making a FOSS app yourself, it needs to be something you need or want to make. If you try to make something for other people without fully understanding the requirements you're probably going to lose interest. A lot of the FOSS apps I have made/use are for specific, single use cases like game addons because they interest me at the time.

If you aren't passionate about a thing its really hard to motivate yourself to work on said thing.

If you're making something you want to make a living off of, then naturally treat it like you would a commercial product.

Contribute to the existing project and improve it? Isn't that the FOSS way? Especially if you don't have a connection to the industry. I'm sure the project would be very appreciative.

"Market" implies money, income, trade.

How do you make money from free software? Short answer --- you don't.

There may be a need/desire but there is no real "market" for Open Source.