Hello @Rod At Work ,
As you certainly learned, EDMX usage can be problematic while using EF code first from database will not cause the current issues. A good way to convince others is to work with EF Core Power Tools (if open to using EF Core). You can reverse engineer databases by right clicking on a project and select EF Power Tools, reverse engineer. If something changes in the database e.g. add a new column you can rerun EF Power tools and it will allow you to update the model(s). On a side note, if you are modifying models e.g. adding read-only properties etc you can always use partial classes placed in a different folder than your models and keep the same namespace.
In regards to Entity Framework vs Entity Framework Core, there are more/better way to do things in EF Core although for the most part existing code should port fine.
Example for selecting tables
Some of the configuration options