Gamedev encompass many different sub fields (design, animation, audio), and developers themselves are at different stages of their careers (just starting out, seasoned indie with 3 titles, 20 year AAA veteran), so I doubt a central forum exists where they all talk together.

Personally, I'm learning mostly about marketing and market research at this stage of my career, so I'm currently on:

- https://gamediscover.co/ (paid membership)

- https://howtomarketagame.com/

In addition to the above, I subscribe to a bunch of newsletters too, like Derek Lieu, SuperJoost, ICO Steam, etc.

I use Godot, so I'm also on the Godot Discord, and I would post on there once every 2 weeks or so when I'm stuck on something in the engine, but not for much else.

I also use Twitter for gamedev-only (thank goodness), and there are some good discussions happening there too every now and then (e.g. this last night: https://twitter.com/ConorMODonovan/status/151362942886108774...)

You can also join IGDA and seek out a SIG (e.g. I'm on the climate SIG) where you talk about the overlap of gamedev with your special interest.