There is no black/white category of what is direct support though. It's a spectrum. And these are my own personal heuristics, rooted in my experiences and found benefits/drawbacks of my own projects and working with people.
Maybe you’re okay with being treated the way the log4j maintainers are being treated right now. The whole point is that you shouldn’t be! People producing valuable software in their free time and giving it away for free should be treated with respect and that’s not happening right now. We need to find a solution!
Someone using something I have written doesn’t cost me anything, but it also doesn’t create any obligations for me. I don’t need to make my contact info public, or have any interactions with users whatsoever.
log4j accepted donations which is really it’s own thing. Running a charity, which is what it means to get paid full time to maintain OSS, has a host of issues that have little to do with OSS and a lot to do with public relations.
If the biggest or only user is one company and its customers, it’s not really capital O Open.
It also means you’re very restricted in license choices since you otherwise never know if your project might get picked up in the future and used in a proprietary service. This likely means you have to use something like AGPL.