My solution was to set my router to use the DNS server at 1.1.1.3 which blocks adult sites.
https://blog.cloudflare.com/introducing-1-1-1-1-for-families...
https://blog.cloudflare.com/introducing-1-1-1-1-for-families...
I agree. It's not a very robust solution, but it's better than nothing at all .
And it's annoying sometimes. One thing I found is that it somehow forces Google safe-search, which appears to block some non-pornographic search results.