Check out https://www.pirateship.com and consider using their USPS Cubic
Rates option, which prices packages up to 20 lbs based on zone and box
size, up to 0.5 cubic feet (12x12x6, the size of a Priority Mail large
flat rate box). The sizes are 0.1, ...
A date hasn't been set yet, and it's still not clear how this will work.
https://www.ecommercebytes.com/2020/12/09/how-can-ebay-offer-usps-tracking-for-under-a-buck/
