Do I need to file a return if I got an extension but don't owe anything?

[Wednesday4]

I've lived abroad ever since I became a taxpayer. My current country and the US have an agreement to avoid double-taxation. Since I only work local jobs and pay the local country's taxes, and earn way below the US's required amount for filing, I was under the impression that I didn't need to file in the US. I haven't for these past few years and nothing's happened.

This year I thought I should, just to be in the system, and also because I wasn't clear as to whether I'd get a stimulus check. The process turned out to be far more complicated than I expected, and I applied for an extension because I simply didn't have time to figure it all out. However, now I'm not sure whether I needed to bother after all. But since I got the extension, does that now obligate me to file a return, even though I owe nothing? One reason why I'm wondering is that I didn't get a stimulus check, and have learned that I could've submitted a form saying that I'm a non-filer, but it's not recommended that you do this if you file a 2019 return.

[fanfare]

Start with IRS Pub 501.

"If you are a U.S. citizen or resident alien, whether you must file a federal income tax return depends on your gross income, your filing status, your age, and whether you are a dependent."

Your tax due, if any,  is irrelevant.