Nellange is registered by the National Board of Health and Welfare in Sweden; it appears that many courses in Europe require students be in the medical field. This particular service, similarly to microblading, is unregulated and differs by state. (In California, The Board of Barbering and Cosmetology does not regulate microblading, for instance.)
Looking into certification courses in America, most do not require students to be a medical professional to be trained in or administer plasma skin tightening. Currently, there is a $3000 certification course that takes place in Beverly Hills which requires one day of online training and a second day with professional supervision while student train on models.
With any aesthetic procedure, it's important to research who will be doing the treatment and how long they have been practicing. For plasma fibroblast, if you're going to see someone outside of a dermatologist or plastic surgeon's office, ask them to provide proof of when they were certified and if they are a licenced esthetician, registered nurse, etc. Typically certifications and licences should be displayed for clients to easily see. (This is also helpful for treatments like microblading, micropenning, chemical peels, etc.)