None! The whole point is that buying one and finding out after the fact that it doesn't work is a crummy plan. I'd like to know what the facts are instead of doing trial and error purchasing.

It's not a fiction that SOME UPS models and portable power stations shut down under low load. This is noted in the links I gave previously. Sometimes this "no-load shutdown" feature can be disabled, e.g., https://www.se.com/in/en/faqs/FA280865/ and sometimes it can't.

Sometimes people faced with this problem (having already shelled out money for a UPS) resort to electronic hacks to solve the problem.

To make things more confusing, sometimes the manufacturer (APC) says specifically that the UPS will shut down under low load, but users say it doesn't happen, and others say it happened to them. Need I mention that random sites on the internet do not always provide 100% reliable information? That's why I asked here, because I think it might be a bit more trustworthy.

And that's why I am interested in people's personal experiences with particular named UPS models that they personally have verified will run a 5W load. I did that with the big expensive and heavy one I have for my computer, as I mentioned above. But I'm looking for a cheaper solution that can be permanently installed next to my VoIP box.