I've been using nextdns and I like it: for one thing, it can tell you the amount of blocked DNS queries, but it's also very helpful for troubleshooting since you can see the log of what was blocked, when, and why (which blocklist). You can then completely disable the blocklist, or whitelist specific entries if you prefer. It's a level of customization that I don't believe other DNS adblockers provide since many of them are designed to "just work".