Program.cs

using Microsoft.EntityFrameworkCore;
using Npgsql;
using Npgsql.NameTranslation;

var context = new Ctx();

/*
CREATE TYPE enum_encounter_batch_item_status AS ENUM ('Invalid', 'Processed');

create table "Items"
("Id" integer not null,
 "Status" enum_encounter_batch_item_status not null);
 */

var encounterBatchItems = new[]
{
    new EncounterBatchItem
    {
        Id = 777,
        Status = EncounterBatchItemStatus.Invalid,
    },
    new EncounterBatchItem
    {
        Id = 888,
        Status = EncounterBatchItemStatus.Processed,
    }
};

context.Items.AddRange(encounterBatchItems);
await context.SaveChangesAsync();

public enum EncounterBatchItemStatus
{
    Invalid,
    Processed
}

public class EncounterBatchItem
{
    public long Id { get; set; }
    public EncounterBatchItemStatus Status { get; set; }
}

class Ctx : DbContext
{
    public Ctx(DbContextOptions options) : base(options)
    {
    }

    public Ctx()
    {
    }

    public DbSet<EncounterBatchItem> Items { get; set; }

    protected override void OnConfiguring(DbContextOptionsBuilder optionsBuilder)
    {
        NpgsqlConnection.GlobalTypeMapper
            .MapEnum<EncounterBatchItemStatus>("enum_encounter_batch_item_status", new NpgsqlNullNameTranslator());

        optionsBuilder.UseNpgsql("Server=127.0.0.1;Port=5432;Userid=postgres;Password=***;Database=postgres");
    }
}