I write a lot of my own software and open source it. And very few of those projects ever have/get any contributions from anyone else. In fact, most of the recent ones literally only have one commit out on Gitlab. And it's pretty rare that I contribute to existing open source projects.

Many years ago, I contributed as part of my job a fair amount to a some WYSIWYG documentation writing web app associated with the Gentoo project. I think that web app is long-since dead and gone. (Not my fault, I promise. Lol.)

Oh, also, I wrote a lot of code as part of the same job that I was always promised would be open sourced, but I kindof had to leave without pushing that issue and that code hasn't ever been open sourced. It's bullshit that still bothers me today, but there's nothing really that I can do about it now. The place is out of business. I could theoretically contact the guy who was in charge (he would have inherited all of that company's intellectual property and would have the right to open source it now), but that guy's the kind of person I'd much rather never have any contact with again. It's a whole thing.

Since then, nothing concrete I can think of.