Needing a static IP address (for accessing my home network through a VPN server) I found out that Cloudflare offers a DNS record update API which can effectively replace the need for a third-party DDNS Provider (e.g. noip).
opkg update
opkg install ddns-scripts-cloudflare luci-app-ddns
opkg install wget ca-certificates
opkg install curl ca-bundle
Create an API Token with Zone > Zone > Read and Zone > DNS > Edit Permission . If you own a domain you can also set Include> Specific Zone> yourdomain.com.
If you want to use a subdomain of your domain your-domain.com, say home.your-domain.com then the configuration can be set via UCI as follows
uci set ddns.cloudflare=service
uci set ddns.cloudflare.service_name='cloudflare.com-v4'
uci set ddns.cloudflare.use_ipv6='0'
uci set ddns.cloudflare.enabled='1'
uci set ddns.cloudflare.lookup_host='home.your-domain.com’
uci set ddns.cloudflare.domain='[email protected]’
uci set ddns.cloudflare.username='Bearer'
uci set ddns.cloudflare.password='CLOUDLARE-API-TOKEN’
uci set ddns.cloudflare.use_https='1'
uci set ddns.cloudflare.cacert='/etc/ssl/certs'
uci set ddns.cloudflare.interface='wan'
uci set ddns.cloudflare.use_syslog='2'
uci set ddns.cloudflare.check_unit='minutes'
uci set ddns.cloudflare.force_unit='minutes'
uci set ddns.cloudflare.retry_unit='seconds'
uci set ddns.cloudflare.ip_source='web'
uci set ddns.cloudflare.ip_url='https://api.ipify.org'
uci set ddns.cloudflare.check_interval='10'
uci set ddns.cloudflare.force_interval='30'
uci commit ddns
If you want to use a different web source from api.ipify.org to fetch your public IP from your router there are many options, like ifconfig.me, icanhazip.com.