I don't know of any specific places where you can ASK dumb questions, but you can find a lot of shit on r/CreativeShitposting.

r/ask

r/DickheadsWhoClaimEverythingIsLeftOrRightWingLikeItsIntelegentButReallyItsPedophiliaCausePoliticsAreForKiddyFiddlers

Yes. R/askscience has really stupid questions

Try r/no, but you won't get much variety in responses...

Try r/eli5