Glad that solved it , so in short the connection using your ethernet interface was already configured by you to use google dns servers but the connection using your wifi interface was using the dns server provided by your router which then get it's dns from your isp. Since you weren't able to access www.videolan.org, I can only assume that your traffic was going through the connection using your wifi interface. Now we also changed the connection using your wifi interface to use google dns servers and you are able to access www.videolan.org. So your ISP is blocking www.videolan.org on dns level. Can you share the output of the following just so I can see the difference as to what you got before?
$ host www.videolan.org
www.videolan.org has address 126.96.36.199
www.videolan.org has IPv6 address 2a01:e0d:1:3:58bf:fa02:c0de:5