They just launched the esim beta today a select list of compatible phones. Works on their super lte service which is verizon. You can pick any of the unlimited plans or the custom plans. Good thing is that plans can be as inexpensive as $5 though you don't get much for that.
iPhone SE 2020
iPhone 11,11 Pro,11 Pro Max
iPhone XS,XS Max
iPhone XR
Google Pixel 4a