In the inadyn-mt version for 7.2 release you find a note related to freedns.afraid.org.
Check your inadyn-mt version:
@vuduo2:~# inadyn-mt --version
Wed Dec 25 22:18:44 2019: W:LANG: Cannot open language file. Will use english defaults, or default override (--lang_file <path/file_name>...)
Wed Dec 25 22:18:44 2019: Version: 02.24.44
In current version (02.24.44) that server (freedns.afraid.org) is supported by the program.
In the case you can try changing the program start command in the related init script, as the note suggests.
@vuduo2:~# inadyn-mt --help
Wed Dec 25 22:46:08 2019: W:LANG: Cannot open language file. Will use english defaults, or default override (--lang_file <path/file_name>...)
INADYN-MT Help
INADYN-MT is a dynamic DNS client. That is, it maintains the IP address
of a host name. It periodically checks whether the IP address of the current machine
(the external visible IP address of the machine that runs INADYN) has changed.
If yes it performs an update in the dynamic dns server.
Typical usage:
-for dyndns.org system:
inadyn-mt -u username -p password -a my.registrated.name
-for freedns.afraid.org:
inadyn-mt --dyndns_system default@freedns.afraid.org -a my.registrated.name,hash -a anothername,hash2
'hash' is extracted from the grab url batch file that is downloaded from freedns.afraid.org