it looks like another 'web' server "light tpd" was installed or started and it is using the http port 80, which is what pigs/dvr requires.The above text seems imply another pigs is running. I have run the stop command without success. Below is the result of the 'sudo Isof -i :80' command.
[email protected]:~/pigs $ sudo lsof -i :80
COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME
lighttpd 541 www-data 4u IPv4 17264 0t0 TCP *:http (LISTEN)
lighttpd 541 www-data 5u IPv6 17265 0t0 TCP *:http (LISTEN)
you need to disable or uninstall that.
The pigs log messages are a little deceiving (needs to be fixed) it said it could not bind to port 80 (true), then it said serving on port 80 (its not)
and googling a little, i'm guessing you installed Pi-Hole, which seems to install lighttpd. There is a way to change the port that pi-hole listens on in one of its config files. change the pile-hole config file to port say 8080 instead of 80 , reboot, then pi-hole will be available
then to access pi-hole you'd type <some ip>:8080 to get to its UI
someone did it here a while back. maybe you can search for that post...
actually @Alainl12 gave you that answer directly in this post Running Pi-Hole with PiGS