Linkedin job posts have a free tier which means a posting can be left up indefinitely whether the search is active or not. Indeed posts cost a minimum $5/day, so a given company would likely take the listing down if their search is not active. I've heard that Linkedin is actively resume harvesting, for what reason I don't really know (maybe training some resume AI?) so it could just be a rumor, but I have a chip on my shoulder about Linkedin anyways for trying to make a pay-to-win job search platform.

Whatever you do, don't apply at the individual job board. Go to the company's careers page to see if its even still posted and apply there. For whatever that's worth (not much in my experience).