Try to update Pihole FTL to 6.0 version and got this:
[✓] Enabling lighttpd service to start on reboot...
[✓] Checking for user 'pihole'
[i] FTL Checks...
[✓] Detected x86_64 processor
[i] Checking for existing FTL binary...
[i] Downloading and Installing FTL...curl: (22) The requested URL returned error: 404
[✗] Downloading and Installing FTL
Error: URL https://github.com/pi-hole/ftl/releases/latest/download/pihole-FTL-linux-x86_64 not found
[✗] FTL Engine not installed
Please upload a debug log and post just the token URL that is generated after the log is uploaded by running the following command from the Pi-hole host terminal:
✗] dig return code: 9
[✗] dig response: ;; communications error to 205.251.193.151#53: connection refused
[✗] Error: dig command failed - Unable to check OS
[✗] Failed to resolve doubleclick.com via a remote, public DNS server (8.8.8.8)
I would first sort the DNS issues of the host, then try the update again.
There is no DNS issue, I do all local DNS resolution with secure forwards to quad9 via stubby. All other port 53 traffic, DoH, and DoT requests are blocked.
This error has only occurred with my second pi-hole instance. The first instance updated to 6 just a short while ago without any problems (same OS, same config, same VLAN).
And the error is a 404 - server side error. So either the URL just changed within the last few minutes and the install / update script is now broken, or github is throttling requests.