Unity is very tricky for importing NuGet packages. Need to very careful and using only .NET Standard 2.0 or 2.1 versions of the NuGet packages. Also, EntityFrameworkCore requires database provider, such as SQLite provider to work properly. That triggers another chain of dependencies to include. Each platform has a unique sub-set of dependencies. To be honest that is really time consuming to make all of that to work.

That is why I made the bundle package, that would include all required dependencies for Unity project to let it work at least on these platforms: Windows, Android, iOS, MacOS. There is the bundle package - Unity + EFCore + SQLite.

Please let me know if you find any issues, I would be glad to polish it. It works for my project on all the mentioned platforms. Just please make sure you switched project to .NET Standard 2.0 or 2.1 as mentioned in the README.