A lot certainly are, including Spanish ones. However in Spain the ATM's just require a phone # and validate that phone # with a text message. Getting SIMs in Spain without KYC is supposed to be illegal. But there are places that will fill out fake details for you. Also you can get SIM cards in other countries and use them in Spain without registration. Eg I personally have gotten Ukrainian SIM cards without KYC, and used them in Spain with no issues.

For no-KYC the best I've personally seen so far is North Macedonia. While there aren't many ATMs, exchange booths operate openly with no AML/KYC at all. Want $1000 worth? No problem!

Remember that phones can also be tracked by IMEI number. So if you really want to use a burner SIM card securely, you need to also use a burner phone. And if you do that, don't leave your regular phone and burner phone on at the same time! Easy to correlate them by the fact you're connecting to similar cell towers. Very few phones allow you to change IMEI numbers unfortunately - it's a legal requirement that they be fixed in many countries. Should be a legal requirement that they be changeable...