What are possible next steps after the completion of a less-than-stellar PhD?

As Buffy points out, the premise of the question

Clearly, my academic credentials are far from being stellar.

is a bit questionable in your case, as in terms of academic credentials research quality and recommendation letters are likely the most important things, and time to completion and GPA do not really matter.

However, taken at face value, the answer to "what can I do in this situation" is probably that it depends. While you may not have the credentials for a very competitive postdoc, a starting academic position, or a competitive industry research position, you don't describe a situation with truly awful credentials, either (and completion of a PhD in the first place usually indicates an important baseline of expertise). Whether you can continue in each of the directions (1), (2), and (3) depends on some individual factors:

1. Ask my advisor for a position to work on some more papers

This seems like an ideal option if you have a good relationship with your advisor and are excited about continuing this research, as well as continuing in academia, but (in your advisor's estimation), your CV is not strong enough to get postdocs in your area. The plan would be to just spend some extra time to get a couple more papers so that you can get a good postdoc. (Incidentally, I'm not sure what the position would formally be, but I guess it would probably be a postdoc.)

2. Apply for postdoctoral positions elsewhere

It is possible this is a good option if the small publication that you have is promising enough, and if your advisor can strongly recommend you without qualifications. You would probably have to ask your advisor unambiguously if they can recommend you enough to get good positions. This is also a better option than (1) (even for a weaker postdoc) if your PhD research is not generally successful or not exciting to you anymore, and you want to switch directions to build a better resume.

3. Apply for industry jobs

What industries are looking for varies by field, and it also depends on if you are looking for research industry or non-research industry. In general for non-research industry, companies are less concerned about sheer number of papers and more about abstract qualities such as work ethic, ability to learn, and knowledge of the basic fundamentals of the field (rather than knowledge of esoteric research topics), so this is a strong option for many people. Note however that if your intention is to go into academia, taking this route (again assuming non-research industry) will not open any new doors, and might close some existing ones.

You are putting up your own roadblocks. Your GPA isn't material if you have a doctorate. The quality of your dissertation might be. The recommendations from your advisor and others might be.

But you should at least apply to a few external places, perhaps both for post docs and for regular positions. If you go to industry it might be hard to return to academia if that is your goal.

But, in the US, at least there are a lot of institutions whose faculty doesn't focus primarily on research. If you can teach and inspire undergraduates then you can probably find a position if you try hard enough.

The conditions and requirements in your "own place" can't be judged here. And much depends on the economy at the time. And now, the pandemic also.

But don't give up before you start.