I would be extremely surprised if I came across meth that had fentanyl intentionally put in it. I cant see anyone cutting a super cheap,plentiful, product, which is easy to produce locally
( methamphetamine) , with a drug that is more expensive, is usually imported, and has its own market with high demand. if it did test positive for fent, Id be willing to bet its either a rare isolated incident, or a result of cross contamination from both substances being transported and/or stored together.
as for all meth being shit, I would honestly say, at least where I am, meth is probably one of the purest street drugs going at the moment. If you are in a country that has free drug testing services, this would be the only sure way to know its purity. even with an acetone wash, there theoretically could be by-products from the synthesis that could dissolve in acetone along with the meth. if you can access a drug testing service, Id advise that. but honestly, in my opinion, if your methamphetamine comes as large shards of crystal, it probably is reasonably pure. powdered crank id be more concerned