Disable certain rows of a Entity Reference Source view

I have a field that is an entity reference on a piece of content. I created a view that is an Entity Reference Source and set the reference type on the field to that view. When editing the content, I see my list of checkboxes using that Entity Reference Source view.

The data in the list are tournaments. Once a tournament is completed, I do not want the user to be able to uncheck that tournament when editing the content. They can only toggle "upcoming" tournaments.

I have tried doing a form alter, but each option in $form['field_tournament']['widget']['#options'] appears to be a Drupal\Core\Field\FieldFilteredMarkup so I cant actually disable the row since its just HTML markup which only includes the label, not the checkbox.

function MYMODULE_form_group_league_edit_form_alter(&$form, FormStateInterface $form_state) {
  foreach ($form['field_tournaments']['widget']['#options'] as $key => $option) {
    // disable here if the tournament is set to completed.
  }
}

I understand in the view, I can set to only show "upcoming" tournaments, but I want the ability for them to see which ones have been completed while editing.

So I figured it out using a custom widget and the Form Options Attributes module, although now that I think of it I could have probably achieved the same thing in the form alter since I am just loading the term via the key which I had access to before. Anyway, I searched the code base of how the Check boxes/radio widget was built and copied that and modified the code to add a disabled attribute to the option.

<?php

namespace Drupal\pick_dynasty_golf\Plugin\Field\FieldWidget;

use Drupal\Core\Field\FieldItemListInterface;
use Drupal\Core\Field\Plugin\Field\FieldWidget\OptionsButtonsWidget;
use Drupal\Core\Form\FormStateInterface;

/**
 * Defines the 'pick_dynasty_golf_tournament_selection' field widget.
 *
 * @FieldWidget(
 *   id = "pick_dynasty_golf_tournament_selection",
 *   label = @Translation("Tournament Selection"),
 *   field_types = {
 *     "boolean",
 *     "entity_reference",
 *     "list_integer",
 *     "list_float",
 *     "list_string",
 *   },
 *   multiple_values = TRUE
 * )
 */
class TournamentSelectionWidget extends OptionsButtonsWidget {

  /**
   * {@inheritdoc}
   */
  public function formElement(FieldItemListInterface $items, $delta, array $element, array &$form, FormStateInterface $form_state) {
    $element = parent::formElement($items, $delta, $element, $form, $form_state);
    // Get all options.
    $options = $this->getOptions($items->getEntity());
    // Get already selected options.
    $selected = $this->getSelectedOptions($items);
    $tids = [];
    // Use the key from the $options to get term IDs (the tournaments).
    foreach ($options as $tid => $option) {
      $tids[] = $tid;
    }
    // Load all the tournaments.
    $term_storage = \Drupal::entityTypeManager()->getStorage('taxonomy_term');
    $terms = $term_storage->loadMultiple($tids);
    $disabled = [];
    // Loop through them and disable any tournament with a status of 'post'
    foreach ($terms as $term) {
      $status = $term->get('field_tournament_status')->value;
      if ($status == 'post') {
        $disabled[$term->id()] = [
          'disabled' => TRUE,
        ];
      }
    }

    $element += [
      '#type' => 'checkboxes',
      '#default_value' => $selected,
      '#options' => $options,
      '#options_attributes' => $disabled, // This is from the Form Options Attributes module.
    ];

    return $element;
  }

}

One BIG issue I did not consider was if the field is disabled (even if previously selected) it does not get submitted so I lose the value. readonly on check boxes is not an option. I basically have to disable it in JS unfortunately and write a custom validator on the backend that checks that no disabled items were added/removed