RT-AC86U Override ISP DNS in USB WAN?

[helloguys]

I have a RT-AC86U and using dual WAN. For the primary WAN (Ethernet), there's an option to use customized DNS server instead of the ISP's DNS (see screenshot). However, I couldn't find corresponding settings in secondary WAN (USB). Is there a solution? Thanks!

 

[metahome]

I realise that this is a very old post, but did you ever get an answer? I have exactly the same issue today.

 

[L&LD]

The user hasn't been on the forums for almost exactly a year. And with almost 1,000 views and no response, it doesn't seem to have an answer either.