Online web emulators used to not work on tablets like the iPad due to how keyboard commands were handled. A few years ago I was working with an online emulator and the author confirmed it wasn’t possible due to the mobile browsers only sending keys, instead of “key X down, key X up” sequences (or something like that).
To my surprise, when I checked the JS Mocha CoCo emulator today, it worked on the iPad with a bluetooth keyboard! At some point, something changed and it is now possible to use an external keyboard on a tablet (at least an iPad) and use the emulators. I also spot checked the XRoar Online emulator and it works too, but since it does not currently support keyboard translation, you have to know where the CoCo keys are on a modern keyboard.
Check it out, and please let me know if this also works on android tablets.