There are several mobile games of the Sonic the Hedgehog series available on iOS or Android, whether being ports of older games or original experiences specifically designed for mobile phones.

Most of these are official games, but this website will feature some unofficial ones (mainly focusing on pixel-art style platformers)

You can find these apps on Google Play: https://play.google.com/store/apps/dev?id=7891990035506213180&hl=en_US

or on iOS: https://apps.apple.com/us/developer/sega/id281966698