CRUD apps don't really get open-sourced for several reasons:
(1) CRUD apps tend to be commercial or internal -- most people don't build CRUD apps for fun -- so they're heavily IP-protected.
(2) CRUD apps tend to be highly specific to the way a particular company or department does something, and then require lots of customization on top of that, and then usually don't do their job very well anyway. You wouldn't be able to just grab the code and database schema from the internal support department of some company and use it in your own as-is.
(3) People haven't figured out how to make them highly reusable, such that you could pull a library from NuGet and add a full column of CRUD functionality to another CRUD app. (They haven't figured it out because they're trained in awful, simplistic database practices and design inflexible, fragile, uncuttable, single-use databases, and then design their entire application as a simple layer around that database. And yes, I'm talking about you, dear reader. It's actually astonishing how backward the current standard of database design is.)
That all being said, an actually well-designed, fully fleshed-out CRUD app would be very useful as a reference. Tutorials just never even scratch the surface.
Re (3): Such comments always tickle my curiosity and my thirst for knowledge. So, which books, courses, codebases do you recommend for both beginners and us with beginner's mind that would help us design and build databases which are the opposite of what you describe?
(1) CRUD apps tend to be commercial or internal -- most people don't build CRUD apps for fun -- so they're heavily IP-protected.
(2) CRUD apps tend to be highly specific to the way a particular company or department does something, and then require lots of customization on top of that, and then usually don't do their job very well anyway. You wouldn't be able to just grab the code and database schema from the internal support department of some company and use it in your own as-is.
(3) People haven't figured out how to make them highly reusable, such that you could pull a library from NuGet and add a full column of CRUD functionality to another CRUD app. (They haven't figured it out because they're trained in awful, simplistic database practices and design inflexible, fragile, uncuttable, single-use databases, and then design their entire application as a simple layer around that database. And yes, I'm talking about you, dear reader. It's actually astonishing how backward the current standard of database design is.)
That all being said, an actually well-designed, fully fleshed-out CRUD app would be very useful as a reference. Tutorials just never even scratch the surface.