Mozzilla Firefox Help -This device is using NextDNS with no profile. Make sure you use the DNS-over-HTTPS endpoint shown below.

I am running Firefox on Linux Mint Cinnamon - I had it all set up with no error messages and now when I logged in I got this message.

I followed the Mozilla set up as best I could - however, there is no "check Enablle DNS over HTTPS choice in settings that allows me to tick or toggle as instructed below, therefor I cannot enter the string provided.

I did change the network.ttr to 3 form 0, but then changed it back when I couldn't change the rest of the settings.

Open Preferences.

2. Scroll down to the Network Settings section and click on Settings.

3. Scroll down and check Enable DNS over HTTPS.

4. Select Custom, enter https://dns.nextdns.io/2863fb and click OK.

5. Enter "about:config" in the address bar (and click on I Accept the risk! if asked).

6. Set network.trr.mode to 3.

With this error, performed test.nextdns.io and got the following results:
    "status": "ok",
    "protocol": "DOH",
    "client": "12.247.235.122",
    "srcIP": "12.247.235.122",
    "destIP": "45.32.219.28",
    "anycast": false,
    "server": "vultr-atl-1",
    "clientName": "trr"

When I ran ping.nextdns.io I got these results:

■ vultr-atl        27 ms  (anycast1, ultralow1)
  zepto-xrs        53 ms
  teraswitch-pit   56 ms
  tier-clt         59 ms
  zepto-iad        59 ms
  anexia-mnz       68 ms
  router-pit       79 ms
  hetzner-iad     100 ms
  anexia-atl      108 ms  (anycast2, ultralow2)
  hydron-clt       error

Any help is greatly appreciated!

Please be gentle....I'm new at this and Linux