php - I want to select all Users which are not members of a Group with id=6

Solution:

If you want to select users who don't have a relation, you can use whereDoesntHave:

$users = User
    ::whereDoesntHave('groups', fn($query) => $query->where('id', 1))
    ->get();

In this case I'm querying for all users who dont have a group with id 1 linked.

Solution:

public function show(Group $group)
{
    //Fetching all members of the group
    $exceptId = $group->users()->pluck('users.id');

    return Inertia::render('Clients/Show', [
            //Here it will fetch all users except those with ids matching $exceptId array
            'users' => Group::whereNotIn('id', $exceptId)->get(),
    ]);
}