I've just finished '100days of SwiftUI' course!!

However, I'm going to make an app similar to Goodnotes5 and Notability, it seems that SwiftUI is not enough, it's necessary for me to learn UIKit now?

Thanks!

Why is SwiftUI not enough? Please do explain what functionality it is that you're looking to implement that cannot be done using SwiftUI. Maybe someone will be ale to help you how to move forward without having to start leaning UIKit

If you're making an app that needs a highly customized user interface and fast graphics, UIKit might be a better choice. SwiftUI, on the other hand, might be a better option if you're creating an app that needs to run across a variety of Apple devices.

Yes please do it, companies still prefer UIKit and people who are experienced in those companies have worked primarily on UIKit , also its not that bad an idea to learn UIKit after doing SwiftUI, actually its more helpful, so in short yes in the job market its a necessity as of now.