Pihole wont load after updating

There are 2 different issues:

1. The web interface files are missing

Your debug log shows the files couldn't be found:

*** [ DIAGNOSING ]: Web version
git status failed

Please try to repair the installation running sudo pihole -r.

If the repair attempt works, try to fix then next issue.

2. Two different web servers trying to use the same port:

Your debug log shows that you are running Pi-hole v6.4.2:

*** [ DIAGNOSING ]: Core version
[✓] Version: v6.4.2

(...)

*** [ DIAGNOSING ]: FTL version
[✓] Version: v6.6.1 

These URLs are not used by your Pi-hole.

Your log also shows lighttpd is using port 80. Pi-hole v6 doesn't use lighttpd or PHP. This was changed since Pi-hole v6.0.

Now, Pi-hole v6 uses its own web server.

The settings show Pi-hole is configured to use ports 80 and 443 (not port 8080), but lighttpd is already using port 80, so this port won't show Pi-hole web interface.