What social media sites or communities are the best to share your PH launch with?

Indiehackers is a good one

Indie hacker is quite good. There is a quite big overlap between both audiences.

congrats on the launch! I'm looking for some channels too :) I was thinking reddit - there's a couple of threads https://www.reddit.com/r/Product...

I think you want to think about who would care about your product, and share it there. For example a developer tool will be relevant to developers, so you should share your developer tool on LinkedIn, Reddit, IndieHackers, and other places with lots of developers.