XFCE Did Not Automatically Pick Up DNS Servers from Router?

I’ve got a pi-hole running on my network, and my router’s DNS is pointed directly there. All other devices that have DHCP enabled automatically pull their DNS from the router, go to the pi-hole, and see no ads.

Much to my astonishment, when I opened up Chromium in XFCE, there were ads everywhere. I used the Network applet in the bottom menubar thing to manually set the DNS to the pi-hole in both IPv4 and IPv6, and all the ads disappeared.

Is this the expected default behavior? Shouldn’t having everything set to auto, the way it comes on a clean install, automatically get the proper DNS addresses from the router/gateway address? I know it was getting valid IP addresses from the router, and the connection was working before I did anything. Just not the correct DNS. I’m very confused.

I just realized I forgot to check the resolv.conf file to figure out what the values were before I changed them. Sorry about that.

Well talking about expected default behavior, my current install had no problem getting the DNS server from my modem.
In mean time i have changed my setup to run my own DNS server to block ads domains, so i don’t know about the current default.
I installed this like a month ago using Architect…

On second read, I shouldn’t have actually replied. resolve.conf is however where I’d look first too, to check what is determining the DNS on that device, and with regards to what to expect as default I’d start here.