On iOS there was at least at some point a "shake to undo" or a 3 fingered swipe I could never get to trigger, infuriating, I just live without undo now.
The 3 finger tap is infuriatingly hard to trigger for me since if you don’t sync your fingers’ taps perfectly, you’re tapping random elements on the screen, potentially doing something bad, like saving/sending out the bad change, that you were trying to undo. A single triple-tap would have been better, but also there is a full SQUARE INCH of wasted space below the iOS keyboard on current phones. Idk why they can’t make use of some of it to open a cut/copy/paste/undo menu, or heck, add command and control keys too!