https/http URLs for the services:
http or https may be used with their respective default ports 80 and 443,
domain names that may be used:

• www.balug.org (dual stack: this service available via IPv4 and IPv6)
  
• www.ipv4.balug.org (this service available only via IPv4)
  
• www.ipv6.balug.org (this service available only via IPv6)
  

Note that in the above, if the www. prefix is omitted, will HTTP redirect to include the www. prefix.

So, e.g:
https://www.balug.org/myip http://www.balug.org/myip
https://www.ipv4.balug.org/myip http://www.ipv4.balug.org/myip
https://www.ipv6.balug.org/myip http://www.ipv6.balug.org/myip

domain names that may be used:

• balug.org (dual stack: this service available via IPv4 and IPv6)
  
• ipv4.balug.org (this service available only via IPv4)
  
• ipv6.balug.org (this service available only via IPv6)
  

Note that the above may optionally be prefixed by www.
user / login name, use myip, e.g. ssh -T myip@balug.org or ssh -l myip -T balug.org
There is no password and password is neither needed nor requested.
No pseudo-terminal allocation will not occur, so may want to use -T option or equivalent option/setting.
For ssh fingerprints, see DNSSEC secured DNS SSHFP records, for many clients, may also be able to use, e.g.:
ssh -T -o VerifyHostKeyDNS=yes myip@balug.org
One may also want to put suitable configuration options in ~/.ssh/config or equivalent, e.g.:

Host balug.org balug.org. ipv4.balug.org ipv4.balug.org. ipv6.balug.org ipv6.balug.org. www.balug.org www.balug.org. www.ipv4.balug.org www.ipv4.balug.org. www.ipv6.balug.org www.ipv6.balug.org.
User myip
RequestTTY no
VerifyHostKeyDNS yes

One can then conveniently do something like just: ssh balug.org
In all output cases, the output is terminated by a single newline character.

One may give a single command matching exactly one of these:

• myconnection
• SSH_CONNECTION

in which case the output is instead of just the first value from SSH_CONNECTION from the environment,
the full content of SSH_CONNECTION from the environment, which is described on ssh(1):

SSH_CONNECTION        Identifies the client and server ends of the con-  
                      nection.  The variable contains four space-sepa-  
                      rated values: client IP address, client port num-
                      ber, server IP address, and server port number.

E.g.:

$ ssh -T -o VerifyHostKeyDNS=yes myip@balug.org myconnection
96.86.170.226 53136 96.86.170.229 22
$ ssh -T -o VerifyHostKeyDNS=yes myip@ipv6.balug.org SSH_CONNECTION
2001:470:67:76f::2 58882 2001:470:1f05:19e::2 22
$ 

Various URL query parameters that may be accepted.
For http/https URLs/interface as noted further above,
with http or https, and one of those noted domains, and with path portion of /myip
that path portion can be followed by query parameters.
those start with an initial ? and then each subsequent parameter is separated from other by &
E.g. one could use:
/myip?list
to get a list, or
/myip?help
to get help, or
/myip?submit to submit an entry, etc.

…

help is exclusive and takes no value(s)

Lots of documentation still to be done here:
submit URL, domain, or IP address
notes
protocol https http dns ssh telnet
httpsport 443, httpport 80, dnsport 53, sshport 22, telnetport 23
class IN, type TXT
user