Why not use https://ipinfo.io/ip instead? It returns just the IP, so you don't need the web-skip option (which feels really hacky).

Didn't know that! 😢

If you want to set multiple options you have to use double quotes. Example:

set service dns dynamic interface eth0 service custom-cloudflare options "zone=yourdomain.com use=web ssl=yes ttl=1"

Incase this helps someone with debugging...

Make sure you change the interface above to the correct one e.g. if you are in the UK you could well be on a provider like BT that still uses pppoe - so you'll probably want the pppoe0 interface instead of eth0.

Cloudflare issues: the current version of ddclient is v3.8.3 (for Edge Router 4 with v2.0.9 firmware). This old version of ddclient doesn't work with the new cloudflare api tokens, so you must use the old global api key token instead.

v3.9.x versions of ddclient should work with the newer api tokens so have a check to see what the ddclient version your firmware is using is:

/usr/sbin/ddclient --version

For me I was having unhelpful errors in tail /var/log/messages like this:

Feb  1 20:39:24 ubnt ddclient[1234]: WARNING:  file /var/cache/ddclient/ddclient_eth0.cache, line 3: Invalid Value for keyword 'ip' = ''

and show dns dynamic status was giving noconnect e.g.

interface    : eth0
ip address   : 
host-name    : dns.example.com
last update  : Tue Feb  1 01:02:03 2022
update-status: noconnect

You can find out which part of the process is failing by calling ddclient directly. To get some debug output use the following (change the conf filename to match the interface you are using e.g. eth0 or pppoe0 etc):

sudo /usr/sbin/ddclient -daemon=0 -debug -verbose -noquiet -file /etc/ddclient/ddclient_eth0.conf

You can edit your ddclient.conf with for example (change the file name to eth0 to pppoe0 or whatever interface you are using):

sudo vi /etc/ddclient/ddclient_eth0.conf

This'll make it easy to try different settings and fix your issue. If it's not using your new config try removing the cache file e.g. sudo rm /var/cache/ddclient/ddclient_eth0.cache (remember to change the filename to match your interface again).

Once you've got it working, update your setup with update dns dynamic interface eth0.

A working setup will give show dns dynamic status with:

interface    : eth0
ip address   : 1.2.3.4
host-name    : dns.example.com
last update  : Tue Feb  1 01:02:03 2022
update-status: good

Thank you @kule! I was struggling getting dynamic DNS to work on my ER-X running EdgeOS v1.10.11 and your comment helped me figure it out. Had to switch to the Global API key and also use "api.cloudflare.com/client/v4" for the server instead of "www.cloudflare.com" like I had seen on other write-ups.