I've been using Blockada for many years but that's a firewall against ads and trackers. No ads inside apps.
Ideally I would use NetGuard to block the apps and Blockada to block ads and trackers for the apps that I allowed to perform network traffic in NetGuard. But Android allows only one active VPN and they can't be chained, so it's a hard choice. Actually it's not so hard: I keep blocking ads and trackers.
Blockada is most likely a DNS level blocker, netguard supports that. Alternatively you can configure it to point the DNS servers at NextDNS if you just want a nice UI to configure block lists (though NextDNS might track you).
NextDNS as a manual DNS server on Android is the adblocking solution I've been using for years. Is there any reason to believe they would track you, any more than any other DNS provider?
Ideally I would use NetGuard to block the apps and Blockada to block ads and trackers for the apps that I allowed to perform network traffic in NetGuard. But Android allows only one active VPN and they can't be chained, so it's a hard choice. Actually it's not so hard: I keep blocking ads and trackers.