Short list of 'useful' slack groups (and one linkedin group)

I saw the list on here the other day of 400 slack groups. I scanned through and mostly were very small or niche. But I ended up joining 3 new ones that look good with big populations and so far lots of intelligent non-spammy talk. I've also shown a couple I'm already a member of which I recommend...

See you in there and say hello ;-)

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