These are tools with drastically different use-cases. In short, no - NextDNS does not eliminate the need for Lockdown. They accomplish very different things.
Lockdown disables features and technologies that could be used in direct attacks to break into your device.
NextDNS filters web traffic and will give you finer control over what domains your device connects to. (Be-it for really any reason you’re chasing for: Privacy/security/ads/etc.)
Just as NextDNS won’t do much to prevent malicious fonts from loading in your browser (as lockdown does), Lockdown doesn’t add any additional protection when it comes to which domains your device connects to. (as nextDNS does)
Got it, that makes a lot more sense! I wasn’t able to find a list of what Lockdown uses for its filtering, but yes in principal NextDNS can replace Lockdown - ‘in principal’ because I’m unclear what blocklists Lockdown is using and if you can perfectly replicate it via NextDNS, though I’m sure with the countless blocklist options on NextDNS and the additional features it’ll likely outperform Lockdown.
One advantage Lockdown has is it’s fairly easy to use Lockdown alongside most iOS VPNs via the two-VPN configuration. Whereas NextDNS doesn’t natively work alongside VPNs, and you have to hope your VPN supports custom DNS.
I did exactly that. I noticed Lockdown App was not blocking Apple Ads even after I manually added the domains to the App, which is annoying (and suspicious…)
I now use NextDNS with the NextDNS ads/tracker block list, the Apple telemetry block list, as well as all of their security setting turned on. I HIGHLY recommend NextDNS. Having such granular control over the traffic going to/from all of my devices as well as the added security has been really nice. Also its pretty cheap.
The trade off is like Henry mentioned, using it with a VPN is a chore and not possible for ProtonVPN at this time. I made the choice to use NextDNS most of the time and for specific use cases (like traveling and using public WiFi) I turn on ProtonVPN but otherwise stick with NextDNS. I was having other issues using an always on VPN with banking sites not liking ProtonVPN servers and my Tesla app failing to connect.