Based on the error message you provided, it seems that the issue is related to the file ownership and permissions. Although you have set the file permissions to 755 for folders/directories and 644 for files, this configuration only allows the owner to write to the folders. In most cases, PHP might not be the owner of the folder, which prevents the plugin from creating the necessary files.
To resolve this issue, I recommend updating the permissions to 775 for folders/directories and 664 for files. This configuration grants write access to both the owner and the group, which should allow the plugin to function as intended.
You can update the permissions using the following commands:
sudo find /var/www/wordpress/wp-content -type d -exec chmod 775 {} \;
sudo find /var/www/wordpress/wp-content -type f -exec chmod 664 {} \;
After applying these changes, please try using the All-in-One WP Migration plugin again and see if the issue is resolved