Query QueryBuilder with NOT IN and usage in controller - symfony

Question

After several weeks of research, I turn to you to try to understand the QueryBuilder part and implement it on my application.
Concretely, here is what I would like to do:
Depending on the agent(s) chosen by the user, display targets with the same nationality.
My agent entity and my target entity each have a nationality. They are both connected thanks to Doctrine on my Mission entity.
I think I should use NOT IN in my request but don't know how to do it. I show you what I did without results.
/**
* Récupère les nationalités de l'agent
*/
public function findNationality()
{
$this
->createQueryBuilder ('m')
->select ('*')
->join('m.agents', 'a')
->join('m.cibles', 'c')
->where('a.nationality = c.nationality')
->getQuery()
->getResult();
}
My MissionType
public function buildForm(FormBuilderInterface $builder, array $options): void
{
$builder
->add('title')
->add('description')
->add('code_name')
->add('country')
->add('speciality', EntityType::class, [
'label' => 'Choisir une spécialité: ',
'placeholder' => 'Choisir une spécialité',
'class' => Specialite::class,
'choice_label' => 'name'
])
->add('agents', EntityType::class, [
'label' => 'Choisir un ou des agent(s): ',
'class' => Agent::class,
'choice_label' => 'identification_code',
'multiple' => true,
'expanded' => true
])
->add('contacts', EntityType::class, [
'label' => 'Selectionner le(les) contact(s): ',
'class' => Contact::class,
'choice_label' => 'code_name',
'multiple' => true,
'expanded' => true
])
->add('cibles', EntityType::class, [
'label' => 'Selectionner la(les) cible(s): ',
'class' => Cible::class,
'choice_label' => 'code_name',
'multiple' => true,
'expanded' => true
])
->add('planques', EntityType::class, [
'label' => 'Selectionner la(les) planque(s): ',
'class' => Planque::class,
'choice_label' => 'code',
'multiple' => true,
'expanded' => true,
])
->add('start_date', DateType::class, [
'widget' => 'single_text'
])
->add('end_date', DateType::class, [
'widget' => 'single_text'
])
->add('status', EntityType::class, [
'label' => 'Statut de la Mission: ',
'class' => Status::class,
'choice_label' => 'name'
])
->add('type', EntityType::class, [
'label' => 'Type de Mission: ',
'class' => TypeMission::class,
'choice_label' => 'name'
]);
}
My Mission Entity
class Mission
{
/**
* #ORM\Id
* #ORM\GeneratedValue
* #ORM\Column(type="integer")
*/
private $id;
/**
* #ORM\Column(type="string", length=255)
*/
private $title;
/**
* #ORM\Column(type="text")
*/
private $description;
/**
* #ORM\Column(type="string", length=255)
*/
private $code_name;
/**
* #ORM\Column(type="string", length=255)
*/
private $country;
/**
* #ORM\Column(type="date")
*/
private $start_date;
/**
* #ORM\Column(type="date")
*/
private $end_date;
/**
* #ORM\OneToMany(targetEntity=Agent::class, mappedBy="mission", cascade={"persist", "merge"})
*/
private $agents;
/**
* #ORM\OneToMany(targetEntity=Cible::class, mappedBy="mission", cascade={"persist", "merge"})
*/
private $cibles;
/**
* #ORM\OneToMany(targetEntity=Contact::class, mappedBy="mission", cascade={"persist", "merge"})
*/
private $contacts;
/**
* #ORM\OneToMany(targetEntity=Planque::class, mappedBy="mission", cascade={"persist", "merge"})
*/
private $planques;
/**
* #ORM\ManyToOne(targetEntity=Specialite::class, inversedBy="missions", cascade={"persist", "merge"})
*/
private $speciality;
/**
* #ORM\ManyToOne(targetEntity=Status::class, inversedBy="missions", cascade={"persist", "merge"})
*/
private $status;
/**
* #ORM\ManyToOne(targetEntity=TypeMission::class, inversedBy="missions", cascade={"persist", "merge"})
*/
private $type;
public function __construct()
{
$this->agents = new ArrayCollection();
$this->cibles = new ArrayCollection();
$this->contacts = new ArrayCollection();
$this->planques = new ArrayCollection();
}
I would like the list of targets to update dynamically according to the choice of agents.
Any help will be welcome and I thank you in advance because I admit going around in circles and no longer know where I am.