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Are Internet boards and Forums dead
(lemm.ee)
This is a most excellent place for technology news and articles.
Depends on the subject, though they are definitely nowhere near as popular nor used anywhere near as much as in the past. Niche groups can probably be found, but I wouldn't know too much about where to look since I usually don't go to them.
Closest I go to is Steam Underground and that is just for certain files.