DNS66: OSS ad blocker for Android that works for all apps (no root needed)
github.com
github.com
If you want more features like per-app internet control, different profiles for wifi/lte/roaming, per app logging, etc then NetGuard is for you:
https://github.com/M66B/NetGuard
note: hosts based blocking is only included in the pro plugin in the github version due to Google restrictions in the play store.