I remember reading somewhere that this workaround can be useful:
- Create listings on business directories such as YP, CitySearch and Yelp.
Google will then automatically create a Maps listing for your business using that information, within 24-48 hrs.
Verify that Maps listing with your website's Search Console email address. This way, you (probably) won't need postcard verification.
How would you go about verifying a business in GMB without postcards?