You have a modified version of the web part of Pi-hole installed. Perhaps related to your Apache configuration.
*** [ DIAGNOSING ]: Web version
[i] Web: v4.3.3 (https://discourse.pi-hole.net/t/how-do-i-update-pi-hole/249)
[i] Branch: master
[i] Commit: v4.3.3-0-g62f2ffc-dirty
[i] Status: M .github/ISSUE_TEMPLATE.md
M .github/PULL_REQUEST_TEMPLATE.md
M .gitignore
M .pullapprove.yml
M .user.php.ini
...
Let's try this to repair your current install:
sudo rm /var/www/html/admin
sudo git clone https://github.com/pi-hole/AdminLTE.git /var/www/html/admin
pihole -r and select repair