New installation fails

Try reverting to master and then try FTLDNS again

sudo rm /etc/pihole/ftlbranch
pihole checkout master

same result

ZBOX ~ # rm /etc/pihole/ftlbranch
ZBOX ~ # pihole checkout master
Please note that changing branches severely alters your Pi-hole subsystems
Features that work on the master branch, may not on a development branch
This feature is NOT supported unless a Pi-hole developer explicitly asks!
Have you read and understood this? [y/N] y

[i] Shortcut "master" detected - checking out master branches...
[i] Pi-hole core
[✓] Switching to branch: 'master' from 'refs/heads/master'
[i] Already up-to-date.
[i] Web interface
[✓] Switching to branch: 'master' from 'refs/heads/master'
[i] Already up-to-date.
[✓] Detected x86_64 architecture
[✓] Installing FTL
ZBOX ~ # echo “FTLDNS” | sudo tee /etc/pihole/ftlbranch
“FTLDNS”
ZBOX ~ # pihole checkout core FTLDNS
Please note that changing branches severely alters your Pi-hole subsystems
Features that work on the master branch, may not on a development branch
This feature is NOT supported unless a Pi-hole developer explicitly asks!
Have you read and understood this? [y/N] y

[i] Branch change has been cancelled

Please try pihole checkout FTLDNS -x and reply with the output

ZBOX ~ # pihole checkout FTLDNS -x
Please note that changing branches severely alters your Pi-hole subsystems
Features that work on the master branch, may not on a development branch
This feature is NOT supported unless a Pi-hole developer explicitly asks!
Have you read and understood this? [y/N] y

[i] Requested option "FTLDNS" is not available

Sorry my mistake pihole checkout core FTLDNS -x

ZBOX ~ # pihole checkout core FTLDNS -x
Please note that changing branches severely alters your Pi-hole subsystems
Features that work on the master branch, may not on a development branch
This feature is NOT supported unless a Pi-hole developer explicitly asks!
Have you read and understood this? [y/N] y

[✗] Fetching branches from https://github.com/pi-hole/pi-hole.git

What does locale return?

Also try this

  1. sudo nano /etc/resolv.conf
  2. change 127.0.0.1 to 8.8.8.8
  3. save
  4. re run pihole checkout core FTLDNS -x

Thank you for your patience

ZBOX ~ # nano /etc/resolv.conf to 8.8.8.8
Edit: reboot resets to 127.0.0.1
but I tried the FTLDNS-Chack out before

ZBOX ~ # pihole checkout core FTLDNS -x
  Please note that changing branches severely alters your Pi-hole subsystems
  Features that work on the master branch, may not on a development branch
  This feature is NOT supported unless a Pi-hole developer explicitly asks!
  Have you read and understood this? [y/N] y

  [✗] Fetching branches from https://github.com/pi-hole/pi-hole.git

So here is where we are at I honestly have no idea why when we set you system resolver to google you are failing to retrieve the git branches could you run locale and paste the output here? We have seen some issues with languages causing errors with the git side of things

I will change locales and will try different forwarders

Change locale to en (english) not sure what your native language is)

my native language is german. I will try to change US

now I changed (also log-out / log-in ssh-session.
ZBOX ~ # locale
LANG=en_US.UTF-8
LANGUAGE=
LC_CTYPE=en_US.UTF-8
LC_NUMERIC="en_US.UTF-8"
LC_TIME="en_US.UTF-8"
LC_COLLATE="en_US.UTF-8"
LC_MONETARY="en_US.UTF-8"
LC_MESSAGES="en_US.UTF-8"
LC_PAPER="en_US.UTF-8"
LC_NAME="en_US.UTF-8"
LC_ADDRESS="en_US.UTF-8"
LC_TELEPHONE="en_US.UTF-8"
LC_MEASUREMENT="en_US.UTF-8"
LC_IDENTIFICATION="en_US.UTF-8"
LC_ALL=

ZBOX ~ # pihole checkout core FTLDNS -x
Please note that changing branches severely alters your Pi-hole subsystems
Features that work on the master branch, may not on a development branch
This feature is NOT supported unless a Pi-hole developer explicitly asks!
Have you read and understood this? [y/N] y

[✓] Fetching branches from https://github.com/pi-hole/pi-hole.git
[i] 31 branches available for Pi-hole Core

[✓] Switching to branch: 'FTLDNS' from 'refs/heads/master'
[i] Already up-to-date.
[i] Running installer to upgrade your installation

[✓] Root user check

    .;;,.
    .ccccc:,.
     :cccclll:.      ..,,
      :ccccclll.   ;ooodc
       'ccll:;ll .oooodc
         .;cll.;;looo:.
             .. ','.
            .',,,,,,'.
          .',,,,,,,,,,.
        .',,,,,,,,,,,,....
      ....''',,,,,,,'.......
    .........  ....  .........
    ..........      ..........
    ..........      ..........
    .........  ....  .........
      ........,,,,,,,'......
        ....',,,,,,,,,,,,.
           .',,,,,,,,,'.
            .',,,,,,'.
              ..'''.

[i] Testing for port 53 availability...
Port 53 is in use by dnsmasq.
In order for the installer to proceed, dnsmasq needs to be disabled.
Please re-run the installer with the following command:
curl -sSL https://install.pi-hole.net | bash -s -- --skip-DNS-port-check

there we are... and now?

Please run sudo /etc/.pihole/automated\ install/basic-install.sh --skip-DNS-port-check

same result as before... frustrating. DNS-Resolution ist broken.

> ZBOX ~ # /etc/.pihole/automated\ install/basic-install.sh --skip-DNS-port-check
    > 
    >   [✓] Root user check
    > 
    >         .;;,.
    >         .ccccc:,.
    >          :cccclll:.      ..,,
    >           :ccccclll.   ;ooodc
    >            'ccll:;ll .oooodc
    >              .;cll.;;looo:.
    >                  .. ','.
    >                 .',,,,,,'.
    >               .',,,,,,,,,,.
    >             .',,,,,,,,,,,,....
    >           ....''',,,,,,,'.......
    >         .........  ....  .........
    >         ..........      ..........
    >         ..........      ..........
    >         .........  ....  .........
    >           ........,,,,,,,'......
    >             ....',,,,,,,,,,,,.
    >                .',,,,,,,,,'.
    >                 .',,,,,,'.
    >                   ..'''.
    > 
    >   [i] Testing for port 53 availability...
    >    Port 53 is in use by dnsmasq.
    >   --skip-DNS-port-check flag was used. The installer will disable dnsmasq after dependencies and packages
    >   have been downloaded, and replace dnsmasq with FTLDNS.
    >   [i] Existing PHP installation detected : PHP version 7.0.30-0ubuntu0.16.04.1
    >   [i] Update option selected
    >   [✓] Disk space check
    > 
    >   [✓] Update local cache of available packages
    > 
    >   [✓] Checking apt-get for upgraded packages... up to date!
    > 
    >   [i] Installer Dependency checks...
    >   [✓] Checking for apt-utils
    >   [✓] Checking for dialog
    >   [✓] Checking for debconf
    >   [✓] Checking for dhcpcd5
    >   [✓] Checking for git
    >   [✓] Checking for iproute2
    >   [✓] Checking for whiptail
    > 
    >   [✓] Check for existing repository in /etc/.pihole
    >   [✓] Update repo in /etc/.pihole
    > 
    >   [✓] Check for existing repository in /var/www/html/admin
    >   [✓] Update repo in /var/www/html/admin
    > 
    >   [i] Main Dependency checks...
    >   [✓] Checking for bc
    >   [✓] Checking for cron
    >   [✓] Checking for curl
    >   [✓] Checking for dnsutils
    >   [✓] Checking for iputils-ping
    >   [✓] Checking for lsof
    >   [✓] Checking for netcat
    >   [✓] Checking for psmisc
    >   [✓] Checking for sudo
    >   [✓] Checking for unzip
    >   [✓] Checking for wget
    >   [✓] Checking for idn2
    >   [✓] Checking for sqlite3
    >   [✓] Checking for libcap2-bin
    >   [✓] Checking for dns-root-data
    >   [✓] Checking for resolvconf
    >   [✓] Checking for lighttpd
    >   [✓] Checking for php7.0-common
    >   [✓] Checking for php7.0-cgi
    >   [✓] Checking for php7.0-sqlite3
    > 
    >   [✓] Enabling lighttpd service to start on reboot
    >   [✓] Installing scripts from /etc/.pihole
    > 
    >   [i] Installing configs from /etc/.pihole...
    >   [i] Existing dnsmasq.conf found... it is not a Pi-hole file, leaving alone!
    >   [✓] Copying 01-pihole.conf to /etc/dnsmasq.d/01-pihole.conf
    > 
    >   [i] Installing blocking page...
    >   [✓] Creating directory for blocking page, and copying files
    >   [✗] Backing up index.lighttpd.html
    >         No default index.lighttpd.html file found... not backing up
    > 
    >   [✓] Installing sudoer file
    > 
    >   [✓] Installing latest Cron script
    > 
    >   [✓] Installing latest logrotate script
    > 
    >   [i] FTL Checks...
    >   [✓] Detected x86_64 architecture
    >   [i] Checking for existing FTL binary...
    >   [✓] Downloading and Installing FTL
    >   [i] FTL can now resolve DNS Queries without dnsmasq running separately
    >   [✓] Stopping dnsmasq service...
    >   [✓] Disabling dnsmasq service
    > 
    >   [✓] man pages installed and database updated
    >   [i] Checking if dnsmasq is enabled
    >   [✓] Disabling dnsmasq from restarting when Network manager starts/restarts
    >   [✓] Restarting Network manager
    >   [i] Checking if dnsmasq is still running
    >    dnsmasq still active, this is most likely due to the fact that dnsmasq
    >     was loaded via a non convetional method. This might cause future conflicts with FTLDNS


> ZBOX ~ # pihole -v
>   Pi-hole version is v3.3-405-g415608f (Latest: v3.3.1)
>   AdminLTE version is v3.3 (Latest: v3.3)
>   FTL version is v3.0 (Latest: v3.0)

Alright i know this is frustrating but trust me it is helping us troubleshoot and helping us track down the issues

Please run

echo release/v4.0 | sudo tee /etc/pihole/ftlbranch 
pihole checkout core release/v4.0 
pihole checkout web release/v4.0

I am very grateful for your patience and support. I hope I will not infect you with my frustration.
But there is no end.

ZBOX ~ # echo release/v4.0 | sudo tee /etc/pihole/ftlbranch
release/v4.0
ZBOX ~ # pihole checkout core release/v4.0
Please note that changing branches severely alters your Pi-hole subsystems
Features that work on the master branch, may not on a development branch
This feature is NOT supported unless a Pi-hole developer explicitly asks!
Have you read and understood this? [y/N] y

[i] Branch change has been cancelled

I also tried different kinds of yYjJ

Did your locale change back during reboot? we have found that Git does not like languages other than english as it returns things our scripts do not expect

no. still on en_US.UTF-8

ZBOX ~ # locale
LANG=en_US.UTF-8
LANGUAGE=
LC_CTYPE=en_US.UTF-8
LC_NUMERIC="en_US.UTF-8"
LC_TIME="en_US.UTF-8"
LC_COLLATE="en_US.UTF-8"
LC_MONETARY="en_US.UTF-8"
LC_MESSAGES="en_US.UTF-8"
LC_PAPER="en_US.UTF-8"
LC_NAME="en_US.UTF-8"
LC_ADDRESS="en_US.UTF-8"
LC_TELEPHONE="en_US.UTF-8"
LC_MEASUREMENT="en_US.UTF-8"
LC_IDENTIFICATION="en_US.UTF-8"
LC_ALL=

Try closing your terminal window, re-open it and re-run the command.

The installer behaves like that when anything but y is entered there.