Also have the same issue.
root@DietPi:~# pihole -up
[i] Checking for updates...
[i] Pi-hole Core: up to date
[i] Web Interface: up to date
[i] FTL: update available
[i] FTL out of date, it will be updated by the installer.
[✓] Root user check
.;;,.
.ccccc:,.
:cccclll:. ..,,
:ccccclll. ;ooodc
'ccll:;ll .oooodc
.;cll.;;looo:.
.. ','.
.',,,,,,'.
.',,,,,,,,,,.
.',,,,,,,,,,,,....
....''',,,,,,,'.......
......... .... .........
.......... ..........
.......... ..........
......... .... .........
........,,,,,,,'......
....',,,,,,,,,,,,.
.',,,,,,,,,'.
.',,,,,,'.
..'''.
[✓] Update local cache of available packages
[i] Existing PHP installation detected : PHP version 7.3.19-1~deb 10u1
[i] Performing unattended setup, no whiptail dialogs will be disp layed
[✓] Disk space check
[✓] Checking apt-get for upgraded packages... 1 updates available
[i] It is recommended to update your OS after installing the Pi-h ole!
[i] Installer Dependency checks...
[✓] Checking for dhcpcd5
[✓] Checking for git
[✓] Checking for iproute2
[✓] Checking for whiptail
[✓] Checking for dnsutils
[✗] Unsupported OS detected: Raspbian GNU/Linux 10 (buster)
https://docs.pi-hole.net/main/prerequesites/#supported-operat ing-systems
e.g: If you are seeing this message on a fresh install, you c an run:
'curl -sSL https://install.pi-hole.net | PIHOLE_SKIP_O S_CHECK=true sudo -E bash'
If you are seeing this message after having run pihole - up:
'PIHOLE_SKIP_OS_CHECK=true sudo -E pihole -r'
(In this case, your previous run of pihole -up will have already updated the local repository)
If that is the case, you can feel free to ask the community o n Discourse with the Community Help category:
https://discourse.pi-hole.net/c/bugs-problems-issues/communit y-help/
Unable to complete update, please contact Pi-hole Support