When a zone has several shipping methods, which one is picked for the customer first?

At checkout the Shipping method list shows the zone's enabled methods in the same order as on the zone's edit page, and the first one is selected automatically. The customer can tap another before paying.

To make Standard the default, it has to be first in the list:

1. Go to Plugins → Shipping Zone and click Edit on the zone.
2. Under Shipping methods, note the settings of the methods above Standard, click Remove method on them, then add them again with + Add method so they come after it.
3. Click Save zone.

Methods with Enabled unticked are not shown at all.