On my android, I cannot type - the keyboard does not open. So it's read-only on my mobile.
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 am able to get the keyboard to pop up if I long press and select something, like copy, from the menu. But I assume they keyboard is supposed to open easier than that. I'm using Galaxy A50, Android 11, Firefox 121 (latest).
As someone who just hit tsdiagram for the first time on my phone, I'll suggest you'd be much better off with an explanatory landing page.
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.