[Ginger-Pickles]

For great justice, does anyone know of any applications (other than Maple) that support WYSIWYG typeset input (not output) like Maple does?

As far as I know, Wolfram/Mathematica, LaTex, SymPy, Jupyter, Sage etc all rely on typewriter text for composing and inputting math. For this (and only this) reason, Maple is the only application that ever resonated with me, because input may be written in the same form it's written by hand, and it's baffling this capability isn't more commonplace. Is this a barrier to anyone else?

[unicas]

There's a lot of them. In principle every CAS that has a TeXmacs interface can do it (FriCAS, Maxima, Reduce ... oo). E.g. https://news.ycombinator.com/item?id=19465270.

[cashsterling]

MathCad works this way also, IIRC.