One of the recent Craft updates (something close to 3.1.25) also brought a redactor migration (https://github.com/craftcms/redactor/blob/v2/src/migrations/m190225_003922_split_cleanup_html_settings.php), which fails when those 2 configs are disabled:
'allowAdminChanges' => false, 'useProjectConfigFile' => false, The reason why it fails is that the migration tries to do something with projectConfig, which is read only when allowAdminChanges is disabled.
According to P&T this is expected behavior. Their solution is to put this in config/app.php:
'components' => [ 'projectConfig' => function() { $config = craft\helpers\App::projectConfigConfig(); $config['readOnly'] = false; return Craft::createObject($config); }, ], (Thanks Oli, Brandon, Andris!)
Since I do all migration via Craft's console commands, this shorter solution works for me:
'allowAdminChanges' => (php_sapi_name() === 'cli') It simply enables admin changes when using the console command.