This device is using NextDNS with another profile.

Thanks R P M 

I get the following:

$ sudo netstat -plunt | grep ":53 "
tcp        0      0 127.0.0.53:53           0.0.0.0:*               LISTEN      1242/systemd-resolv
tcp        0      0 127.0.0.1:53            0.0.0.0:*               LISTEN      9690/nextdns
udp        0      0 127.0.0.1:53            0.0.0.0:*                           9690/nextdns
udp        0      0 127.0.0.53:53           0.0.0.0:*                           1242/systemd-resolv

So where can I go next to get the NextDNS profile?

R P M  yes you're right - I got confused because I kept trying things - and it's similar on another Ubuntu machine -  and now I have stopped the NextDNS service with

nextdns stop

and also run

nextdns deactivate

to make sure it's not doing anything

so when I run 

sudo netstat -plunt | grep ":53 "

I now get 

tcp        0      0 127.0.0.53:53           0.0.0.0:*               LISTEN      1242/systemd-resolv
udp        0      0 127.0.0.53:53           0.0.0.0:*                           1242/systemd-resolv

But when I look at the results from https://www.dnsleaktest.com I get

           IP                                  Hostname                            ISP                                    Country

So somewhere NextDNS is operating to produce this?

R P M 

I'm getting 

$ curl -L https://test.nextdns.io
{
    "status": "unconfigured",
    "resolver": "81.134.97.164",
    "srcIP": "195.213.173.240",
    "server": "anexia-lon-1"
}

This was after completely uninstalling and deactivating NextDNS. And the message on the status page said 

However as soon as I install it with 

$ sudo nextdns install
NextDNS installed and started using systemd init

And then I stop it using and then test the status

$ sudo nextdns stop
$ sudo nextdns status
not installed

I get (anonymised)

$ curl -L https://test.nextdns.io
{
    "status": "ok",
    "protocol": "DOH",
    "profile": "fp0881bfe5356f48ef",
    "client": "195.213.173.241",
    "srcIP": "195.213.173.241",
    "destIP": "45.90.28.09",
    "anycast": true,
    "server": "zepto-lon-1",
    "clientName": "tailscale",
    "deviceName": "upn",
    "deviceID": "ni85CNTRL",
    "deviceIP": "100.123.12.37",
    "deviceModel": "linux"
}

it appears to conflict with Tailscale that's installed on the machine.

And the DNS Leak test shows NextDNS again

                IP                            Hostname                     ISP                                      Country

It had seemed that if I completely uninstalled NextDNS then it would go back to the first curl test above, but I've found that if it is installed and running but deactivated then that's the way to stop the DNS server working.

That didn't appear to be clear to me from the instructions.

The reason I was wanting to stop it from working was when I am using a VPN and don't want any possibility of leaks.

So now I've disabled Tailscale and if I install NextDNS and activate NextDNS i now get a test result that doesn't include the correct profile - a much longer string. The command

nextdns config

shows the correct profile but the test result doesn't, which is very confusing.

How do I get NextDNS to use the correct profile?