I can't use Quad9 as my DNS resolver

[N00bCoderEXE]

For some reason I don't know, when I use Quad9 as my DNS resolver in RethinkDNS, I lose internet access. However, when I use another resolver (like Cloudflare, for example), everything seems to work perfectly. Does anyone know why this happens?

[ignoramous]

It could be that Quad9 is blocked by your ISP?

Also, there were a few issues around Quad9 in prior versions, but it works nicely in v055o, the upcoming version.

[N00bCoderEXE]

Wait, is that possible? Good to know. Regarding my problem: it seems to have resolved itself, I was able to choose Quad9 as my resolver (I think restarting the device had something to do with it).

P.S.: Hey, do you know if it's possible to combine firewall, VPN and Quad9's DNS resolver on the same Android device?

[ignoramous]

you know if it's possible to combine firewall, VPN and Quad9's DNS resolver on the same Android device?

Possible using Rethink, yeah.

Select Quad9 Secure from Configure -> DNS -> Other DNS -> DNS over HTTPS. Then:

If your VPN provider supports exporting WireGuard configuration (like Proton, Mullvad, and Windscribe do, for instance), you can import them into Rethink from Configure -> Setup WireGuard -> tap on the + floating action button in the bottom right corner -> Import (either via QR code or file or manually type the config out).

Make sure Rethink is in DNS + Firewall mode (tap on the downward arrow next to the START / STOP button on Rethink's homescreen).