KS1 Why are you turning browser DNS off? Leave it on the default option and it will use your systems DNS.
If you're looking for a good DNS service then use NextDNS, it has multiple benefits outside of just blocking ads. Run a VPN and use Private DNS settings and link it to Next DNS. Not only are you going to be able to block ads with custom blocklists, but you can use it to identify and block application and system telemetry. Use a hardened Brave, Mozilla, etc browser and you'll be good to go.
If you already use a VPN, without an additional DNS provider, then your VPN provider is processing your DNS queries, which theres nothing wrong with that, you just won't have as much customization as you will with next. If you're using neither a VPN nor third party DNS provider, your ISP is handling your DNS queries. Using NextDNS as a Private DNS host (on top of a VPN), allows you to do the aforementioned ^ and you'll still have the benefits of using the VPN (geolocation spoofing, encrypted traffic, etc).