In the UK we have many people on the left with these perspectives. It comes from the second-wave feminist tradition.

But generally speaking, online age verification is one of those issues where the left-right ideological divide doesn't map neatly. People support and oppose it for various different reasons. Much like the assisted suicide issue.

Age verification efforts in the US have been privacy-attacking (demanding government ID) whereas the system being proposed in europe is privacy-preserving (zero-knowledge proof).