in /etc/backuppc/apache.conf adding these lines solved the issue here:
<Directory /usr/share/backuppc/cgi-bin/> # # 2020-01-07 # after upgrade to buster , when i tried to access the web page for this error: # and in /var/log/apache2/error.log # [Tue Jan 07 16:15:37.112830 2020] [authz_core:error] [pid 20998:tid 139916814022400] [client 172.30.24.115:47886] AH01630: client denied by server configuration: /usr/share/backuppc/cgi-bin/ # You don't have permission to access /backuppc/index.cgi on this server. # these 3 lines fixed the issue # Options Indexes FollowSymLinks AllowOverride None Require all granted PS: I am not sure if that is secure, and there may be a better way to handle the issue.