efcore: scaffolding existing mature db leaves an endless list of model "corrections" - tooling hell & monkey code ... solutions?

I have a large mature database that has been paired with EF 6.4 for years. All relationships properly defined, EF 6.4 was happy and allowed me to utilize the benefits of EF. Never ever had to dig into the bowels of EF and I was glad for the black box experience.

In a different (new framework) application I am using the same database for a NET5.0 Web Api together with EF Core 5.01. I was hoping for the same black box experience, but so far it has been an outright hell with cryptic error messages, endless hours of monkey code , and at least one seemingly unsolvable problem. Wasted weeks of trying different things and made no progress.

This db contains 115 tables, apparently scaffolding cannot determine what the primary keys are in these tables, so I am monkey coding [Key] and “using System.ComponentModel.DataAnnotations;” 115 times over!

Is there a setting I can use so the scaffolding recognizes and put these two items in the correct place for me?

Second, a table called Client has several dependent lookup tables with one-to-many relationships. SSMS shows a nice diagram with keys and many symbols in all the right places, and EF 6.4 was happy! One of the lookup tables is called Gender.

public partial class EqGender
    {
        public EqGender()
        {
            Clients = new HashSet<Client>();
        }

        public int GId { get; set; }
        public string Gender { get; set; }

        public virtual ICollection<Client> Clients { get; set; }
    }`


public partial class Client
    {
        public Client()
        {
            Appointments = new HashSet<Appointment>();
            ...
            Transactions = new HashSet<Transaction>();
        }

        [Key] public int ClientId { get; set; }
        public string Cname { get; set; }
        public string Cdescription { get; set; }
        public int? OwnerLocationId { get; set; }
        public int? EnteredByProviderId { get; set; }
        public int? OwnerBillToId { get; set; }
        public bool? BillLocation { get; set; }

        public int? BId { get; set; }
        public virtual EqGender GIdNavigation { get; set; }
        
        [ForeignKey("EnteredByProviderId")] public virtual Provider EnteredByProvider { get; set; }
        [ForeignKey("OwnerBillToId")]  public virtual Owner OwnerBillTo { get; set; }
        [ForeignKey("OwnerLocationId")] public virtual Owner OwnerLocation { get; set; }
        
        public virtual ICollection<Appointment> Appointments { get; set; }
        public virtual ICollection<Transaction> Transactions { get; set; }
    }

When I query for Client, I get " Microsoft.Data.SqlClient.SqlException (0x80131904): Invalid column name ‘BIdNavigationBId’."

As far as I can see these two Entities are properly setup as per the documentation. What is wrong here?

And I don’t even know if this is the last problem I can expect to have to deal with.