I don't remember 184.108.40.206 ever having an adblock function. Are you sure you're not mistaken?
There are a couple that come to mind...
dns.adguard.com this is one of them from AdGuard that you can use for free.
NextDNS.io it is currently free during its beta phase. After that, you get ad blocking for 300,000 requests per month, and $2 USD/month after that for an unlimited number of requests
Adguard basically installs it and forgets about it. You can't configure it at all. While NextDNS is basically a cloud-based Pi Hole, and you have a lot more configuration options like filter lists to use, whitelists, blacklists, and so on.
If you have an Android device running on Android 9 or higher, you can use its private DNS function and use a service like NextDNS to block ads on your phone
The Iphone can be run on something as small as a PiZero, so this is what I prefer.