If you have a high-end flagship phone (Snapdragon 8 Gen 1 or better), using a Nintendo Switch emulator like Yuzu or Skyline is arguably the most "complete" way to play.
The easiest setup for most players involves streaming the game from a host device. Celeste on Steam
Just remember to breathe. And dash diagonally.
Most platformers are unplayable with touch. Celeste is different. The Everest build includes a feature called —a transparent overlay that shows exactly where your dash will end before you lift your finger.