Set the FRITZBOX_PASSWORD environment variable to the password of your Fritz!Box (FB) and run fritzdump.sh. After a few seconds a browser window/tab with NtopNG should pop up.
If your FB needs a username, set it in FRITZBOX_USERNAME. See fritzdump.sh for more variables to tune and for sharing a configuration file with Fritz!Box Internet Tickets
If you don't have a username because you are using password-only login, then run the script via bash -x and look for the XML snippets. They will show you a username like fritz1234 that you should use.
You can set WIRESHARK=1 to start a local Wireshark instead of NtopNG.
It seems like this is mostly working also with IPv6, happy to get PRs with improvements.