I know this question is probably stupid, but I couldn't find anything for either side. I don't think it's in one of the books that D&D Beyond provides for free. I could also just be blind and not see it.
I'm mainly talking about flight speed and burrow speed, whether it's granted by a spell or by a race: would using the Dash action double flight speed or burrow speed (or swimming speed) given that you have a non-zero number in them?