Installing backuppc from the repository doesn’t result in accessing it over browser by typing http://localhost/backuppc
Instead I had go a step further by appending the following snippet from /etc/backuppc/apache.conf to /etc/apache2/apache2.conf
Alias /backuppc /usr/share/backuppc/cgi-bin/
# Uncomment the line below to ensure that nobody can sniff importanti
# info from network traffic during editing of the BackupPC config or
# when browsing/restoring backups.
# Requires that you have your webserver set up for SSL (https) access.
Options ExecCGI FollowSymlinks
AddHandler cgi-script .cgi
AuthName "BackupPC admin"