$GLOBALS['TCA']['fe_users']['columns']['country']['config'] = [
    'type' => 'select',
    'renderType' => 'selectSingle',
    'itemsProcFunc' => 'My\Extension\UserFunc\TcaProcFunc->staticInfoTablesItems',
    'maxitems' => 1
];

<?php
namespace My\Extension\UserFunc;
 
use TYPO3\CMS\Extbase\Reflection\ObjectAccess;
 
class TcaProcFunc
{
 
    /**
     * @param array $config
     * @return array
     */
    public function staticInfoTablesItems($config)
    {
        $key = 'isoCodeA3';
        $value = 'shortNameLocal';
        $sortbyField = 'isoCodeA3';
        $sorting = 'asc';
 
        $objectManager = \TYPO3\CMS\Core\Utility\GeneralUtility::makeInstance('TYPO3\CMS\Extbase\Object\ObjectManager');
        $countryRepository = $objectManager->get('SJBR\StaticInfoTables\Domain\Repository\CountryRepository');
 
        $countries = $countryRepository->findAllOrderedBy($sortbyField, $sorting);
        $countryList = [];
        $countryList[] = ["", ""];
        foreach ($countries as $country) {
            /** @var $country \SJBR\StaticInfoTables\Domain\Model\Country */
            $countryList[] = [ObjectAccess::getProperty($country, $value), ObjectAccess::getProperty($country, $key)];
        }
        $config['items'] = $countryList;
        return $config;
    }
 
}

if (TYPO3_MODE === 'BE') {
    // Page module hook - show flexform settings in page module
    $extensionName = \TYPO3\CMS\Core\Utility\GeneralUtility::underscoredToUpperCamelCase($_EXTKEY);
    $pluginSignature = strtolower($extensionName) . '_pi';
    $GLOBALS['TYPO3_CONF_VARS']['SC_OPTIONS']['cms/layout/class.tx_cms_layout.php']['list_type_Info'][$pluginSignature][$_EXTKEY] =
        'My\Extension\Hook\CmsLayout->getExtensionSummary';
}

namespace My\Extension\Hook;
class CmsLayout
{
    public function getExtensionSummary(array $params) {
        $result = null;
        if (strpos($params['row']['list_type'], 'myextension_') !== FALSE) {
            $pluginName = str_replace('myextension_', '', $params['row']['list_type']);
            if ($params['row']['pi_flexform'] != '') {
                $this->flexformData = \TYPO3\CMS\Core\Utility\GeneralUtility::xml2array($params['row']['pi_flexform']);
            }
            $methodName = 'bePreview' . ucfirst(GeneralUtility::underscoredToLowerCamelCase($pluginName));
            if (method_exists($this, $methodName)) {
                $result = $this->$methodName($params['row']);
            }
        }
        return $result;
    }
 
    protected function getFieldFromFlexform($key, $sheet = 'sDEF') {
        $flexform = $this->flexformData;
        if (isset($flexform['data'])) {
            $flexform = $flexform['data'];
            if (is_array($flexform) && is_array($flexform[$sheet]) && is_array($flexform[$sheet]['lDEF'])
                && is_array($flexform[$sheet]['lDEF'][$key]) && isset($flexform[$sheet]['lDEF'][$key]['vDEF'])
            ) {
                return $flexform[$sheet]['lDEF'][$key]['vDEF'];
            }
        }
 
        return NULL;
    }
 
    protected function bePreviewPi($row) {
        // whatever
        return '';
    }
}

// remove __No wrap__ optgroup
unset($GLOBALS['TCA']['tt_content']['columns']['imageorient']['config']['items'][8]);