I tend to check the age difference between the earliest and latest commits because that lets me be sure it's not a project that someone spent a couple weeks coding up, dropped on github, and then forgot about. I'll also check the issues on there. I'm looking for more closed issues than open ones, but I'll also quickly scan over them to get a rough idea of how many are truly meaningful issues. I also get signals from the readme and docs. It's not a hard pass if there's issues with those, but it's certainly helpful to my opinion if they exist and are both clear and detailed.
As you indicate though, they require more effort to adjudicate. Are issues from core team members? Are commits meaningful? Is community activity meaningful? I wish GitHub would give allow us to parse things like this more easily.
My use of star count is generally a binary indicator. 1k+ is probably a legit project and below is probably still early. Beyond that, it's probably too noisy.