I'm quite disappointed that even in the year 2022 the best solution HTML offers for rich text editing is the infamous contenteditable attribute.
I can never expect a WYSIWYG editor from a library to work 100% without friction on every platform.
I know it's already near-impossible to implement a web-browser and adding more to the pile of standards/components to implement sounds counter-intuitive. On the other hand, a basic browser that can render just basic HTML and basic CSS is comparatively easy and I would rather have them be able to render a rich-text-field on a low-capability device than being able to do all sorts of JS/CSS magic.
I'm not even against React and all the amazing ecosystem surrounding it - given that your use-case justifies it. I just think auto-completers and rich-text editing and other stuff that nearly every website on this planet re-implements should be standard.
My prediction is that in 2-3 years we will see WASM being used to run desktop class rich text editors in a canvas (much like Google Docs now does), and an open source framework will appear that enables it.
I would even go as far as suggesting WebKit compiled to WASM would be better than trying to make a rich text editor based on contenteditable work everywhere, once you have it working in one version it runs “everywhere”. Although accessibility is going to be the main disadvantage of such system.
Not great for accessibility though (yet)