Lighttpd failing to start after install

From your debug log:

*** [ DIAGNOSING ]: Pi-hole processes
[āœ—] lighttpd daemon is failed

Check this thread for a potential solution: I can't get Pi-hole to work [Ubuntu 18.04] - #10 by RamSet

Also noted in the debug log - the gravity list is empty. Rebuild gravity with pihole -g from the command line.

*** [ DIAGNOSING ]: Gravity list

   -----head of gravity.list------

   -----tail of gravity.list------