Can programmer certifications substitute for a specific degree requirement in a job posting?
The most accurate answer is "it depends".
A more practical answer is "NO".
HR departments and corporate policies that require college degrees will reject you for having no college degree. Not everything in the world is negotiable. I've got an older friend in exactly this situation; he has been programming for 3 decades yet has no college degree and he's finding it harder and harder to get interviewed. 4-5 years ago, he could float a resume on Monday and have interviews by Friday. Now it takes him weeks to get the interviews. He'll be in his 60s before he has a bachelors degree, if he starts right now. I'm 5 years younger than him and I'm working on my 3rd bachelors degree.
Certificates are reasonably good at showing that you keep up with technology - if you get a new cert every couple of years. They are a snapshot showing that you had a certain level of competence in that technology at that time. My first Microsoft cert was in 1998, and I've gotten some of the 4-letter certs every few years since then. As a greybeard, I can show evidence that I didn't rest on my laurels and that I'm keeping up with newer stuff.
In addition, the hardness of credentialism and requirements are only going to get worse in the future:
One of the things that used to happen is that there were HR managers in recruiting who would look at those requisitions and say, “You know, do you really need that? Do you really think you’re going to be able to find somebody like that?” And there was push back. Those people have largely been eliminated through successive downsizing, so there’s nobody there to buffer those expectations. The next thing that happens is those requirements get built into recruiting software, and the recruiting software is a necessary device now, because employers have made it easy to apply for their jobs.
In the past, they wanted lots of applicants, so now they’re overwhelmed by applicants, so now every company will tell you they’re getting thousands or tens of thousands of applicants for positions. You couldn’t possibly screen them all by hand, because you can’t look at them all, so they use automated systems to do the screening. But the screening is never as good as somebody who has human judgment, and the way screening works is you build in a series of typically yes/no questions that try to get at whether somebody has the ability to do this job. And a lot of that ultimately ends up, it’s all you can ask about, is experience and credentials. So you end up with a series of yes/no questions. And you have to clear them all, and I think people building these don’t quite understand that once you have a series of these yes/no questions built in, and the probabilities are cumulative right? You have to hit them all, then you pretty easily end with no one that can fit.
So say that the odds are 50 percent that the typical applicant will give you the right answer in terms of what you’re looking for for the first question, and a 50 percent that they’ll give you the right answer to the second question. Well, then, you’re down to one in four people who will clear those two hurdles, and once you run it out to about 10 questions, it gets you down to about one in 1000 people who would clear those hurdles. And by the way, the first hurdle is usually, What wage are you looking for? And if you guess too high, out that goes, right? So then you’re at the purple squirrel point, where at the end of the day, you find that nobody fits the job requirement. So in the book I describe one anecdote some employer told me about having 25 000 applicants for an engineering job, a reasonably standard engineering job, and the recruiting process indicated none of them were qualified to do the job. How could that happen? Well it’s not that hard once you start building in these yes/no algorithms, and you run out the list, you end up with nobody who can get through.
Source
As an ancedote, one previous employer wanted to rehire me (after I quit to go elsewhere for higher salary). As part of the rehire process, I had to apply online for my old job. The applicant tracking system claimed I didn't qualify for the job I had done for 5 years. So we had to go through a few iterations where the job listing was recrafted and reopened until the software said I was good enough to pass. For a random stranger off the street, that would never have happened - instead the company would have said "we can't get qualified workers."
While you may end up able to get your first programming job with just a certificate, in the long run, the lack of a degree will harm your opportunities. You won't be able to stay "upwind" as Paul Graham puts it.
TL;DR - try to get a first programming job with just the cert, then work on getting your college degree.