I've written a simple script, mainly to query public IPv4 and IPv6 of a computer. Currently about 14 IP-finder services are supported. It also supports fetching local IP and the corresponding network name (like SSID), which is useful for integrations in status-bars of minimal GNU/Linux-based setups like tiling wm desktops.
I've used POSIX sh and tried to fall back to alternative tools if a dependency is not found so the script would be more portable on different Linux distros. Also, it has basic support for Windows via MSYS2.
Hope it's useful. Let me know of what you think ;)