I already know that private DNS is important for privacy. I'm using Quad9 btw.
But recently I hear a lot about NextDNS and similar providers that give more advanced features such as custom filters and domain blocking. I'm getting interested in that topic now as I have to use some proprietary apps with a lot of trackers in them.
However I'm really struggling to find useful information about what domains to block, what settings to use in one or another use case etc. I don't have much experience with firewalls and server stuff either which makes it even harder.
So, could anyone share some good resources on this so I can get started? Or should I just not worry about it and use a whole other system such as firewall?
Well, why don't you just try NextDNS? Don't like signing up to try a service? You don't have to. Go to nextdns.io, click "Try it now" and there you go. No account required for 7 days.
You don't need to add domains yourself, you just choose from existing blocklists they provide. Each have some description, just like all the settings.
Alternatively, Mullvad freely provides DNS with some blocking too, but you can't edit anything.