Asp.net – Where do I put business logic when implementing CQRS pattern using Mediatr in a .Net Clean Architecture application?

Currently I’m facing a trouble implementing the business logic using clean architecture and cqrs pattern. I’m using Mediatr and AutoMapper to do that. I have the following structure for the cqrs pattern

• ApplicationCore
  • DTOs
    • SmartphoneDto.cs
  • Features
    • Smartphone
      • Handlers
        • Commands
          • AddSmartphoneCommandHandler.cs
        • Queries
      • Requests
        • Commands
          • AddSmartphoneCommand.cs
        • Queries
• DomainCore
  • Smartphone.cs

And the following classes:

SmartphoneDto.cs

public class SmartphoneDto
{
    public int Id { get; set; }
    public string serialnumber { get; set; }
}

Domain Entity Smartphone.cs

public class Smartphone
{
    public int Id { get; set; }
    public string imei { get; set; }
    public string serialnumber { get; set; }
    public string calculatedValue { get; set; }

}

AddSmartphoneCommand.cs

public class AddSmartphoneCommand : IRequest<bool>
{
    public SmartphoneDto SmartphoneDto { get; set; }
}

AddSmartphoneCommandHandler.cs

public class AddSmartphoneCommandHandler : IRequestHandler<AddSmartphoneCommand, bool>
{
    private readonly ISmartphoneRepository _smartphoneRepository;
    private readonly IMapper _mapper;

    public AddSmartphoneCommandHandler(ISmartphoneRepository smartphoneRepository, IMapper mapper)
    {
        _smartphoneRepository = smartphoneRepository;
        _mapper = mapper;
    }

    public async Task<bool> Handle(AddSmartphoneCommand request, CancellationToken cancellationToken)
    {
        var smartphone = _mapper.Map<Smartphone>(request.SmartphoneDto);
        //Business Logic???
        await _smartphoneRepository.AddAsync(smartphone);

        return true;
    }
}

And I´m not sure where the business logic goes, I’ve read different post with suggestions like these but with no possible solutions or a clear example:

Post 1 As I understood we can put business logic in a external class that works as a service called from the handle method of the command handler

Post 2 But in this post shows that the command handler doesn’t have to contain any logic.

Due to my confusion, I’ve thinked put the business logic as follow:

{
    private readonly ISmartphoneRepository _smartphoneRepository;
    private readonly IMapper _mapper;

    public AddSmartphoneCommandHandler(ISmartphoneRepository smartphoneRepository, IMapper mapper)
    {
        _smartphoneRepository = smartphoneRepository;
        _mapper = mapper;
    }

    public async Task<bool> Handle(AddSmartphoneCommand request, CancellationToken cancellationToken)
    {
        var smartphone = _mapper.Map<Smartphone>(request.SmartphoneDto);

        #region businesslogic
        //All the business logic in this place
        smartphone.imei = someApi.GetAsync("someurl", smartphone.serialnumber);
        smartphone.calculatedValue = (smartphone.serialnumber - smartphone.imei) * 0.05;
        //end business logic
        #endregion

        await _smartphoneRepository.AddAsync(smartphone);

        return true;
    }
}

What would be the correct place in the structure to put that kind of business logic?