I'm looking for a puzzle rush app that's free and does not require a subscription. I tried using the Chess.com app, but there's a limit on the number of times you can play in a day.
Check out https://blitztactics.com/ which is pretty much the same thing. It even has a few other modes.
I can recommend Max Chess: https://play.google.com/store/apps/details?id=dim.maxym.mychess
You can choose difficulty of puzzles and time mode.