Quad9 is based in Switzerland, but the three founders-sponsors are US-based [0], so I’m not sure if it can be considered 100% safe from US government intervention.

[0] https://quad9.net/about/sponsors/

The ASN and stuff is also operated by a US entity it seems like:

  ASHandle:       AS19281
  Street:         CleanerDNS Inc. dba Quad9
  Street:         1442A Walnut Street, Suite 501
  City:           Berkeley
  State/Prov:     CA
  Country:        US

Also a quick search suggests that Switzerland has made Internet providers in-country block DNS results in the past.