[jcrabtr]

For personal finance and investing, the Bogleheads forum (https://www.bogleheads.org) ticks all the boxes. It definitely has many helpful, knowledgeable participants. Since it's a traditional forum, they maintain civility through moderation, but it isn't needed often.

[ethbro]

Related, Fatwallet Finance also has a pretty decent discussion that spans churning rewards, real estate, and general investment discussion.

https://www.fatwallet.com/forums/finance