TYPO3 Core

I am using EXT:felogin in a v12 site with PHP 8.2 and tried to activate EXT:adminpanel. After clicking to activate it, a TypeError breaks the frontend rendering completely:

rtrim(): Argument #1 ($string) must be of type string, int given

in vendor/typo3/cms-core/Classes/Utility/ArrayUtility.php line 475

calling $key = rtrim($key, '.');

due to vendor/typo3/cms-adminpanel/Classes/Modules/Info/UserIntInformation.php line 79

calling $conf = ArrayUtility::flatten($conf); for this array (typoscript definitions of felogin-Paths):

array(3) {
  ["templateRootPaths."]=>
  array(1) {
    [10]=>
    string(0) "" 
  }
  ["partialRootPaths."]=>
  array(1) {
    [10]=>
    string(0) "" 
  }
  ["layoutRootPaths."]=>
  array(1) {
    [10]=>
    string(0) "" 
  }
}

Apparently this is a problem because the keys of the typoscript definitions of felogin-Paths are not string, but int. Did something change here recently, maybe due to a fluid update?