I am always amazed at the generosity of some people who use free/open-source software. It definitely makes me want to try and become more supportive to such efforts myself.

I make a (closed-source but completely free/ad-free) minimal macOS app for Hue, and every other day (sometimes a week goes by) I get a lovely price-of-a-coffee-sized donation from someone in the community. And when I ask for their name to include them in a credits or supporters panel, most don't even want me to mention it or credit them.

One time, I struggled to replicate an issue for which I didn't have the necessary hardware (multiple Hue bridges), and the bug reporter simply offered to buy and send me "a bunch of bridges and lights" to make debugging easier. I couldn't accept it, but it's gestures like that, combined with positive feedback from people wanting the project to keep going and succeed, that are such a tremendous motivational driver for working on "free stuff". I had totally underestimated that (coming from the SaaS side).