No prescription is required, but as the other comments say, you’re unlikely to learn anything significant.

Blood sugar in non-diabetics is boring, rarely moving in any significant way.

One impact could be dispelling misconceptions if you have them. Another could be discovering pre-diabetes.

I used Libre 3; you can get different ones without a prescription online. You can easily get a prescription (in the US) if you get diagnosed with Type 2 based on your A1C numbers, but ordering a CGM online without any prescription is not a problem at all. Wearing it for 2-4 weeks is usually enough to learn a lot about your relationship with sugar.

I used Stelo from Dexcom with my Oura Ring, no prescription. I didn't really learn much, other than occasionally realizing I was cranky because of low blood sugar.