Hello I am trying to insert data in table as below

    var newClientUsers = new List<Entities.ClientUser>();

    var existingClientUsers = await mycontext.ClientUser.AsNoTracking().ToArrayAsync(cancellationToken: cancellationToken);

    var clientUserList = clientUsers.Select(s =>
        new Entities.ClientUser
        {
            UserName = s.UserName,
            OrganizationId = s.OrganizationId
        }).ToList();

    newClientUsers = clientUserList.Except(existingClientUsers, new ClientUserComparer()).ToList();


    if (newClientUsers.Count > 0)
    {
        await mycontext.ClientUser.AddRange(newClientUsers);
        await mycontext.SaveChangesAsync();
    }
    else
    {
        _logger.LogInformation($"{DateTime.UtcNow} NoClientUsersAdded");
    }

This method fails to add data and gives error

System.InvalidOperationException: The instance of entity type ‘ClientUser’ cannot be tracked because another instance with the same key value for is already being tracked.

However i do not get issue when I remove AsNoTracking() from query or use AddRangeAsync. I want to understand what is the correct scenario for using AsNotracking for inserting data.
if you have any reference please share.