Not ubuntu but mepis, however same issue.

Installed version 3.46.1-1 using Synaptic.

eadwine@mepis12a:~$ webhttrack
/usr/bin/webhttrack(311): launching /usr/bin/x-www-browser
/usr/bin/webhttrack(311): spawning regular browser..
opera: Activated running instance
/usr/bin/webhttrack(311): browser exited
/usr/bin/webhttrack: line 166:   325 Killed                 
${BINPATH}/htsserver "${DISTPATH}/" path "${HOME}/websites" lang "${LANGN}"
$@

I tried <http://mepis12a:8080/server/index.html> in a browser, no dice.

I'll keep looking on the net, but so far nada.