Make sure symfony/flex does not get loaded in a buggy version to avoid bogus issue reports

src/Composer/Plugin/PluginManager.php

@@ -149,6 +149,12 @@ class PluginManager
 
                 return;
             }
+
+            if ($package->getName() === 'symfony/flex' && version_compare($package->getVersion(), '1.9.8', '<')) {
+                $this->io->writeError('<warning>The "' . $package->getName() . '" plugin was skipped because it is not compatible with Composer 2+. Make sure to update it to version 1.9.8 or greater.</warning>');
+
+                return;
+            }
         }
 
         $oldInstallerPlugin = ($package->getType() === 'composer-installer');