Hi @Anonymous ,
PowerApps is highly extensible for pro developers, especially in the form of the developer custom component framework - if you consider components like the map that connects to third party services like Bing, I would guess what you're thinking of is possible, if your target service has an endpoint you can interact with, but I very much doubt you could 'embed' CKEditor5 into your component - but do note I'm doubtful, not certain.
You could possibly build something more feature rich yourself, but that's a lot of effort - It certainly wouldn't be "easy" for a citizen dev like me, but a pro dev should be able to tell you pretty quickly whether it's worth attempting or not.
Lastly, I'm not sure if there is a component framework marketplace to be honest, but the biggest challenges with something like that would be porting across tenants and ensuring the code is vetted and secure. Use of any third party components should also ensure that the overall protection of the content meets the org standards of privacy and security which are already met inside PowerApps/O365.
So I guess the question is - how badly does your customer dislike the OOB solution in terms of your cost of effort to improve it?
[Edit: What features specifically? Maybe there's something in the 365 suite that meets this requirement and integrates well with PowerApps? For example, launching MS Word for users to edit and collaborate in might be an option...]
Kind regards,
RT