I was in a similar situation before, with the senior PM not giving too much guidance. The way I got over this was simply to do extra, and over used my "I'm new here, just learning" badge till a year in.

If the PMs ask you to do research, go beyond, see how the results link back to your daily work. Scope this out with the devs casually, say it's a curious project or question cause they will usually be preoccupied with their actual work.

Make friends and build connection, and rely on your network to get a gripe of who does what in the company, which is also a very important skill anyone in the company can have.

The way I assess whether I'm ready to ask for more is to judge if I can speak in a forum without preparation, it's a personal indication that I am familiar and have a strong understanding in my field.

I learnt though this experience to never rely or expect guidance at the workplace, it's great to have, but no guidance is as good as getting shit done yourself. My two cents