C#
var query = Database.KanbanColumns
    .Where(c => c.ParentBoardId == boardId)
    .OrderBy(c => c.Order)
    .Select(c => new
    {
        Column = c,
        Cards = Database.KanbanCards
            .Where(a => a.ParentColumnId == c.Id)
            .OrderBy(a => a.Order)
            .ToArray()
    });

foreach (var data in query)
{
    yield return new
    {
        column = new
        {
            data.Column.Id,
            data.Column.Color,
            data.Column.Label
        },
        cards = data.Cards
            .Select(a => new
            {
                a.Id,
                Title = a.CardTitle,
                Info = new
                {
                    a.CreatedAt,
                    a.Value,
                    a.Temperature,
                    AssociatedUsers = a.AssociatedUsers
                        .Select(n => AdapterCacheUnit.FetchUser(n))
                        .Where(n => n != null)
                        .Select(n => new
                        {
                            n!.UniqueId,
                            n.UserName,
                            n.ProfilePictureUrl
                        })
                }
            })
    };
}

C#
var query = Database.KanbanColumns
    .Where(c => c.ParentBoardId == boardId)
    .OrderBy(c => c.Order)
    .Select(c => new
    {
        Column = c,
        Cards = Database.KanbanCards
            .Where(a => a.ParentColumnId == c.Id)
            .OrderBy(a => a.Order)
            .ToArray()
    });

foreach (var data in query)
{
    yield return new
    {
        column = new
        {
            data.Column.Id,
            data.Column.Color,
            data.Column.Label
        },
        cards = data.Cards
            .Select(a => new
            {
                a.Id,
                Title = a.CardTitle,
                Info = new
                {
                    a.CreatedAt,
                    a.Value,
                    a.Temperature,
                    AssociatedUsers = a.AssociatedUsers
                        .Select(n => AdapterCacheUnit.FetchUser(n))
                        .Where(n => n != null)
                        .Select(n => new
                        {
                            n!.UniqueId,
                            n.UserName,
                            n.ProfilePictureUrl
                        })
                }
            })
    };
}

System.InvalidOperationException: The LINQ expression 'n => AdapterCacheUnit.FetchUser(n)' could not be translated.
Either rewrite the query in a form that can be translated, or switch to client evaluation explicitly by inserting a call
to 'AsEnumerable', 'AsAsyncEnumerable', 'ToList', or 'ToListAsync'. See https://go.microsoft.com/fwlink/?linkid=2101038
for more information.

System.InvalidOperationException: The LINQ expression 'n => AdapterCacheUnit.FetchUser(n)' could not be translated.
Either rewrite the query in a form that can be translated, or switch to client evaluation explicitly by inserting a call
to 'AsEnumerable', 'AsAsyncEnumerable', 'ToList', or 'ToListAsync'. See https://go.microsoft.com/fwlink/?linkid=2101038
for more information.

static void ApplyGenericConverter(ModelBuilder modelBuilder, Type commonType, Type converterGenericType, int? maxLength = null)
{
    foreach (var entityType in modelBuilder.Model.GetEntityTypes())
    {
        var properties = entityType.ClrType.GetProperties()
            .Where(p => p.PropertyType.IsAssignableTo(commonType));

        foreach (var property in properties)
        {
            var converterType = converterGenericType.MakeGenericType(property.PropertyType.GenericTypeArguments[0]);

            var converter = Activator.CreateInstance(converterType);
            if (converter is null)
            {
                throw new Exception("Error creating the dynamic converter object: " + entityType.ClrType.ToString() + " Property: " + property.ToString());
            }

            var builder = modelBuilder.Entity(entityType.Name).Property(property.Name)
                .HasConversion((ValueConverter)converter);

            if (maxLength is int ml) builder = builder.HasMaxLength(ml);
        }
    }
}

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    ApplyGenericConverter(modelBuilder, typeof(IEntityId), typeof(EntityIdValueConverter<>), maxLength: 26 + 1 + 3);
    ApplyGenericConverter(modelBuilder, typeof(IJsonBox), typeof(JsonBoxValueConverter<>));
}

static void ApplyGenericConverter(ModelBuilder modelBuilder, Type commonType, Type converterGenericType, int? maxLength = null)
{
    foreach (var entityType in modelBuilder.Model.GetEntityTypes())
    {
        var properties = entityType.ClrType.GetProperties()
            .Where(p => p.PropertyType.IsAssignableTo(commonType));

        foreach (var property in properties)
        {
            var converterType = converterGenericType.MakeGenericType(property.PropertyType.GenericTypeArguments[0]);

            var converter = Activator.CreateInstance(converterType);
            if (converter is null)
            {
                throw new Exception("Error creating the dynamic converter object: " + entityType.ClrType.ToString() + " Property: " + property.ToString());
            }

            var builder = modelBuilder.Entity(entityType.Name).Property(property.Name)
                .HasConversion((ValueConverter)converter);

            if (maxLength is int ml) builder = builder.HasMaxLength(ml);
        }
    }
}

protected override void OnModelCreating(ModelBuilder modelBuilder)
{
    ApplyGenericConverter(modelBuilder, typeof(IEntityId), typeof(EntityIdValueConverter<>), maxLength: 26 + 1 + 3);
    ApplyGenericConverter(modelBuilder, typeof(IJsonBox), typeof(JsonBoxValueConverter<>));
}

void Foo(string foo, string? n, object? b) { }
void Foo(string foo, string? n, string? b) { }

public void DoFoo()
{
    Foo("aaa", null, null);
}

void Foo(string foo, string? n, object? b) { }
void Foo(string foo, string? n, string? b) { }

public void DoFoo()
{
    Foo("aaa", null, null);
}