filtering related

AccountContact

class AccountContactUser extends Model
{
    use HasFactory;
    use Filterable;

    /**
     * @var array
     */
    protected $allowedFilters = [
        'sap_id',
        'mobile',
        'email',
        'phone',
        'function_description',
        'valid_to',
    ];

    /**
     * @var array
     */
    protected $allowedSorts = [
        'sap_id',
        'mobile',
        'email',
        'phone',
        'function_description',
        'valid_to',
        'contact.surname',
    ];
    
    public function contact()
    {
        return $this->belongsTo(Contact::class);
    }    
}

AccountContactLayout

TD::make('contacts.contact.name', __('Name'))
    ->sort()
    ->render(function (AccountContactUser $relation) {
        return $relation->contact->name ?? '';
    }),
TD::make('contacts.contact.surname', __('Surname'))
    ->sort()
    ->render(function (AccountContactUser $relation) {
        return $relation->contact->surname ?? '';
    }),

AccountContactScreen

'contacts' => AccountContactUser::with(['account'])
                ->filtersApplySelection(ContactSelection::class)
                ->defaultSort('id', 'desc')
                ->paginate(),

ContactSurnameFilter

<?php

namespace App\Orchid\Filters\Contact;

use Illuminate\Database\Eloquent\Builder;
use Orchid\Filters\Filter;
use Orchid\Screen\Field;
use Orchid\Screen\Fields\Input;

class ContactSurnameFilter extends Filter
{
    /**
     * @var array
     */
    public $parameters = ['surname'];

    public function name(): string
    {
        return __('Surname');
    }

    public function run(Builder $builder): Builder
    {
        return $builder->when($this->request->has('surname'), function (Builder $query) {
            $query->whereHas('contact', function (Builder $query) {
                $query->where('surname', 'LIKE', '%'.$this->request->get('surname').'%');
            });
        });
    }

    /**
     * @return Field[]
     */
    public function display(): array
    {
        return [
            Input::make('surname')
                ->type('text')
                ->value($this->request->get('surname'))
                ->placeholder('Search...')
                ->title(__('Surname')),
        ];
    }
}