When installing metatag version: '8.x-1.19' module, the sub module metatag_extended_perms gets created twice,
once inside a folder named b
Install "drupal/metatag": "1.19.0" via composer, run composer install
This appears to be an issue of composer itself, , for patches like https://www.drupal.org/files/issues/2020-01-17/metatag-n2782797-25.patch → , there are old issues reported in composer for this like https://github.com/cweagans/composer-patches/issues/199 , so any patch which tries creating new directories creates with a b/ prefix.
Closed: works as designed
1.19
Code
The Extended Permissions module was added to the codebase, so there's no need to use a patch to add it. To fix the problem, just remove the patch.