@apparatchik

I think here are two unrelated problems: the OP appears to be having issues loading jQuery (probably a JS general problem), which might be helped by changing $ for jQuery as in the proposed patch.

I, however, have bumped into the issue of the flags not loading, etc. with an error in the setCountry function within mobile-number-form-element.js.

It turns out that sometimes, on first load, the setCountry function gets called with a null value before setting itself correctly to the chosen default value. In those cases, the script breaks and the flags never load, etc.

I will be posting a patch here later today, but wanted to leave a heads up, the quick workaround is to check if the value is null and return the function in other to prevent the errors from breaking the functionality.

as in:

function setCountry(country) {
          if(!country){
            return;
          }

          $input.parents('.country-select').find('.mobile-number-flag').removeClass($input.data('value'));
          $input.parents('.country-select').find('.mobile-number-flag').addClass(country.toLowerCase());
          $input.data('value', country.toLowerCase());

          var options = $input.get(0).options;
          for (var i = 0; i < options.length; i++) {
            if (options[i].value === country) {
              var prefix = options[i].label.match(/(\d+)/)[0];
              $input.parents('.country-select').find('.prefix').text('(+' + prefix + ')');
            }
          }
        }
      

I applied the proposed patch and got the following:

 TypeError: count(): Argument #1 ($value) must be of type Countable|array, string given in count() (line 98 of /home/mmex/public_html/web/modules/contrib/metatag/src/Entity/Me  
  tatagDefaults.php).    

I changed line 98 to check if $tag is of type array:

if (is_array($tag) && count($tag) === 1) {
            return reset($tag);
        } 

I don't know how to create a MR.

In a modern project you would want to have composer.json under version control so others could composer install it, Drupal 10's recommended composer project is still missing a useful gitignore.

The patch works great for the BLT config-import scenario described above: installing from configuration without all the limitations, caveats and inconsistencies of a profile's config install scenario (read: no core.extension support). In our case, we wrote a BLT Task Hook to run on new sites install only, thus, when deploying updates we avoid existing sites configuration from being overwritten by the drush cex/cim cycle.