Tip: Look for the symlink differences:
comm -23 <(ls /etc/apache2/sites-available/ | sort) <(ls /etc/apache2/sites-enabled/ | sort)
Tip 2: Disable all sites
sudo a2dissite “*”
sudo systemctl start apache2
Apache should hopefully start.
Next, do this:
a2ensite “a*”
a2ensite “b*”
Go through whole alphabet and numerics until you find the broken config.
Generic output from Apache is this:
[Mon Sep 15 16:41:59.663726 2025] [core:warn] [pid 13393] AH00111: Config variable ${APACHE_RUN_DIR} is not defined apache2: Syntax error on line 80 of /etc/apache2/apache2.conf: DefaultRuntimeDir must be a valid directory, absolute or relative to ServerRoot
Be warned, this has nothing to do with what AI tells you.