No, there are now CGMs that are available without a prescription as an assistive device for sports. You're not supposed to use those for medical purposes, but you can get them without a prescription.

Heck, you can even get medical-grade Freestyle Libre CGMs without a prescription, if you know where to look -- see https://agelessrx.com/cgm-sensor/ for one example, or https://beyondtype2.org/cgms-without-insurance/ for another.