MikroTik script to loop the pppoe connection until it get the public IP, not NAT IP. And then update the DNS A record on CloudFlare Name Server.

mt-nt-pub-cf-ddns.src

# Mikrotik Script for loop until get the public IP from NT 
# and then set DNS A record to that public IP.
#
# Update WANIF to match your interface name. And all CloudFlare required key and info.
#
# Put this into the ppp profile UP script and assign to pppoe connection
#

:local WANIF "pppoe-1";

:while ( $"local-address" in 100.64.0.0/10 ) do={ 
    :log warning ("$WANIF: Got Private IP ".$"local-address"." Reconnecting the interface...");
    /interface pppoe-client disable $WANIF;
    :delay 10s;
    /interface pppoe-client enable $WANIF;
};
:log info ("$WANIF: Got IP ".$"local-address");
:local IP4NEW $"local-address"

# Cloudflare Dynamic DNS update script
# Required policy: read, write, test, policy
# Configuration ---------------------------------------------------------------------

:local TOKEN "__TokenAPI__"
:local ZONEID "__ZoneID__"
:local RECORDID "__RecordID__"
:local RECORDNAME "__SubDomainName__"

#------------------------------------------------------------------------------------
:local url "https://api.cloudflare.com/client/v4/zones/$ZONEID/dns_records/$RECORDID/"
:local cfapi [/tool fetch http-method=put mode=https url=$url check-certificate=no output=user as-value \
    http-header-field="Authorization: Bearer $TOKEN,Content-Type: application/json" \
    http-data="{\"type\":\"A\",\"name\":\"$RECORDNAME\",\"content\":\"$IP4NEW\",\"ttl\":120,\"proxied\":false}"]

:log info "CF-DDNS: Host $RECORDNAME updated with IP $IP4NEW"