Quad9 is a reasonable choice given the stance on privacy and the similar jurisdiction (Mullvad would probably face the same takedown orders as Quad9), but really anyone who cares about bypassing national blocking orders should run a local caching recursive resolver. Unbound is a great choice.

Unbound can also be used to block malware and advertising domains using shared public lists, or you can build your own list. Your resolver’s DNS queries could be piped through Mullvad or Tor if you want additional privacy.