I purged firefox(*) and deleted /etc/firefox and /usr/lib/firefox, the whole .cache thing and so on as already mentioned in Removing Firefox in Ubuntu with all add-ons like it never existed
After all, I still find "Firefox Web Browser" in All Application and even firefox --version shows me (even after reboot)
Mozilla Firefox 72.0.1.
The command type firefox says
firefox is /snap/bin/firefox
What should I do to completely get rid of it?