Next Cloudflare and Google?
Only in Germany if this stands. Sure, other countries may try to follow suit, then start targeting other third parties who won’t do it “voluntarily.” And then they’ll go after Quad9 for any other site that breaks German law.
My concern is that they will apply more and more pressure on operators of public resolvers until we have no impartial DNS any longer. Particularly Europe likes that sort of “filtering” but that was so far limited to ISPs on national levels. Now they seem to want to take this a step further and make international operators block it.