⭐ Merited by Solosanz (1)
maybe if someone know about decentralized place, feel free to suggest and it might help the mixers. 
There are few decentralized place such as Nostr. Although i've no idea how mixers should promote their service on such place while remain on-topic on place they visit.
Google is not banning mixers and platforms that review and advertise mixers so a user will just have to type the word mixer, unless Google filters out mixer keywords and platforms that advertise and promote mixers, you can still find them here in the mainnet not only on the darknet and other online communities discuss and promote mixers like Reddit.
It wouldn't be fun job for those who tasked to perform SEO, they'll have to compete with other and fake mixers for top search result while remain looking convincing.