EnumRepro.cs

using System.ComponentModel.DataAnnotations;
using System.ComponentModel.DataAnnotations.Schema;
using Microsoft.EntityFrameworkCore;

namespace EnumRepro
{
    public class ReproDbContext : DbContext
    {
        protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
        {
            if (!optionsBuilder.IsConfigured)
            {
                optionsBuilder.UseSqlite(@"Data Source=repro.db");
            }
        }

        public DbSet<Model> Models { get; set; }
    }

    public enum State : byte
    {
        One,
        Two,
        Three
    }

    public class Model
    {
        [Key]
        public int Id { get; set; }

        [Required]
        [Column(TypeName = "tinyint")]
        public State State { get; set; }
    }

    public static class Program
    {
        public static void Main()
        {
            var dbContext = new ReproDbContext();
            dbContext.Database.EnsureDeleted();
            dbContext.Database.EnsureCreated();
            dbContext.Models.Add(new Model());
            dbContext.SaveChanges();
        }
    }
}