In June 2020, Tesla added an aftermarket Model Y Tow Package to their website. Aftermarket meaning it can be added to a Model Y that didn’t come from the factory with a tow package.
Link to Tesla’s Model Y Tow Package here
There is a chart in the owner’s manual on page 72 that discusses trailer towing, and lists the rated tow capacity depending on the wheel package. The 20″ wheel has a lower tow capacity than both the 19″ and the 21″ wheel packages.