The best way to avoid ads on mobile is to not use apps that serve ads. Android firefox can have real ublock origin installed, use that to go to websites rather than using those sites' apps.

DNS adblocking is part of a multi-layered defense strategy. It's defeated by ads being served from the same domain as content. I know that more advanced options like pfblocker allow interrogating "fronting" subdomains to detect those that resolve to an ad-server (e.g. funstuff dot domain dot net actually resolves to eviladtechcompany dot ai) and block them as well and that helps a bit but the best defense is having on-device blockers as well.

There's also a lot more ad tech companies that rapidly deploy domains and subdomains to attempt to overwhelm ad list maintainers and they often succeed for a time in a real back and forth battle.

It's also possible the goodreads app has hardcoded secure DNS servers (that don't use the standard DNS port but often 443) that they use to bypass DNS blocking by resolving their ad domains themselves. In that case you'd want to implement a firewall list of the biggest DNS resolvers (for example like this list here I found with a quick search) and prevent any traffic from within your network from reaching them by either dropping or blocking. Importantly you want to ensure that your DNS resolver can still reach the root servers or whatever you're querying but any other device should be blocked from accessing these. You should also be either redirecting the standard DNS port (53) to your DNS server if locally served or blocking it except for any necessary local DNS servers.

If they serve the ads from the same exact servers (same DNS and IP) as the non-ad content, you cannot block through either DNS or IP-based blocking, i.e. local VPN won't work either.

Ublock origin (works on Android Firefox) can block specific URLs, as well as modify the structure of the websites, which is what you'll have to use. With apps that serve ads through their regular servers, you're out of luck. You'll have to use a different app.

Have you tried using more aggressive blocklists? Unfortunately if the app serves ads through the same host which serves normal content, then it basically defeats DNS ad blocking, which can only block ads when ads are served by a separate host.

On Android I'm using the Adguard Firefox extension, and it seems to work pretty well. There might be some more advanced way to block ads in using ReVanced^[https://patch-explorer.web.app/], but I don't know anything about that.

Edit: https://github.com/hoo-dles/morphe-patches claims it can remove Goodreads ads.

Storygraph is the better option 😘