http://maidzonekwrk4xbbmynqnprq2lu7picruncfscfwmyzbmec6naurhyqd.onion/blog/2025-06-03-ios-web-haptics.html
I tried messing around with this to somehow make it work, but ultimately failed to do so. Until I later had to use cobalt.tools for downloading a video, and to my surprise, their buttons had haptics. Of course, I instantly went to their source code to see how they implemented it, and it was pretty trivial.