Looking for a good mobile porn blocker tool

damn, that's exactly why i asked from nofap moderator to put a sub-forum raleted to this questions only. but do they listen ? hell no... people like you need this information and the moderator of this website are full of excuses not to pin a single post about that...

anyway about your question - i think i got what you need (i use it too), and i am aware that k9 is gone now:
https://www.netsparkmobile.com/en/
netspark is perfect for mobile filtering (windows and ios too, by the way) . but it costs money. per device. sorry mate but the free filtering era is over, with good quality comes a price.
also note that this app filters well but slow the surfing a bit.

i won't stay is this forum for long, so if you found this help about this netspark thing useful and you wanna thank me - i really ask you to help other people find out about this netspark thing, because nofap refuse to pin this information. that's the best "thank you" i will have.

and if you convince a moderator to pin this, that's even better

 

There are a whole host of "less smart phones" that would suit your needs man, the new Nokia 3310 is a dumb phone that can handle most internet based messenger apps but the browser on it is primitive and doesnt stream video well at all, making it impractical for pmo related matters, which means you can have a phone incapable of streaming porn whilst also still being able to use messenger apps and a very basic version of google maps, it's cheap and I've spoke to numerous guys who have bought phones like this, managed to quit porn and then progressed to digital minimalism once they realised they actually dont need to have a smartphone and were happier and more present in life without one