Monaco works fine on mobile, just used it for https://tsdiagram.com
I think that was the problem with Monaco on mobile: the keyboard never worked correctly. That was my experience.
Edit: I don't want to complain, Monaco is superb editor and it would be super if it worked on mobile consistently. But from the github issue, it appears that Microsoft doesn't seem to want to change that.
I can see just enough editor UI stuff on my phone to strongly suspect I'm in your target userbase, but because of screen size issue I can not see enough to have any idea what tsdiagram actually does.