NOTE:Special Note for those thinking about using a French Number on their Dual SIM iPhone 11! You can really only install a single physical Nano SIM in the phone! Therefore before you leave the USA you must contact your carrier and have them change your current plan to use a Digital SIM or eSIM. This change can not be made once you depart the USA. This is as of 3/1/2020, while things may change in the future better to check with AT&T, Verizon, etc. FreeMobile does not offer an eSIM service but may in the future.
Clearly the service is not free, however for those visiting Paris or France and Europe it worth a look.
Check out Freemobile.