Debian 10.5. I got through the full tutorial successfully after much debugging. Here are the steps I took to reproduce.

[Danrancan]

APPIMAGE-BUILDER TUTORIAL (INCLUDING INSTALLATION & DEPENDANCY INSTALLATION) FOR

USE ON A CLEAN INSTALL DEBIAN 10 SYSTEM

INSTALLATION AND DEPENDENCIES

sudo apt install -y python3-pip python3-setuptools patchelf desktop-file-utils libgdk-pixbuf2.0-dev fakeroot cmake git wget qml-module-qtquick-controls2/stable qml-module-qtquick-layouts qtbase5-dev qtdeclarative5-dev libkf5qqc2desktopstyle-dev/stable

Install Optional tool apt-file

sudo apt install apt-file

SymLink gdk-pixbuf-2.0 to /usr/bin

sudo ln -s /usr/lib/x86_64-linux-gnu/gdk-pixbuf-2.0/gdk-pixbuf-query-loaders /usr/bin

Install appimagetool AppImage then make it executable with chmod +x

sudo wget https://github.com/AppImage/AppImageKit/releases/download/continuous/appimagetool-x86_64.AppImage -O /usr/local/bin/appimagetool && sudo chmod +x /usr/local/bin/appimagetool

Install latest tagged debian release of appimage-builder

sudo pip3 install appimage-builder

BUILD CONFIGURATION

Download the simple qt-appimage-template source code from git (you will be building this), and then move into the downloaded source directory.

git clone https://www.opencode.net/azubieta/qt-appimage-template.git && cd qt-appimage-template

Use cmake (which you downloaded up above) to create your appimage install prefix

cmake . -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=/usr

Use cmake to install your build configuration into the Appimage Appdir.

make install DESTDIR=AppDir

RECIPE GENERATION

Generate a recipe file (AppImageBuilder.yml) without verification keys

appimage-builder --generate --log DEBUG

Use nano editor to fill in the missing verification gpg keys

nano -c AppImageBuilder.yml

#REPLACE THE FOLLOWING:

sources:
     - sourceline: deb http://deb.debian.org/debian/ buster main
       key_url: ""
     - sourceline: deb http://security.debian.org/debian-security buster/updates main
       key_url: ""
     - sourceline: deb http://deb.debian.org/debian/ buster-updates main
       key_url: ""

WITH THE FOLLOWING:

sources:
    - sourceline: deb http://deb.debian.org/debian/ buster main
      key_url: http://keyserver.ubuntu.com/pks/lookup?op=get&search=0x04EE7237B7D453EC
      key_url: http://keyserver.ubuntu.com/pks/lookup?op=get&search=0x648ACFD622F3D138
      key_url: http://keyserver.ubuntu.com/pks/lookup?op=get&search=0xEF0F382A1A7B6500
      key_url: http://keyserver.ubuntu.com/pks/lookup?op=get&search=0xDCC9EFBF77E11517
    - sourceline: deb http://security.debian.org/debian-security buster/updates main
      key_url: http://keyserver.ubuntu.com/pks/lookup?op=get&search=0xAA8E81B4331F7F50
      key_url: http://keyserver.ubuntu.com/pks/lookup?op=get&search=0x112695A0E562B32A
    - sourceline: deb http://deb.debian.org/debian/ buster-updates main
      key_url: http://keyserver.ubuntu.com/pks/lookup?op=get&search=0x04EE7237B7D453EC
      key_url: http://keyserver.ubuntu.com/pks/lookup?op=get&search=0x648ACFD622F3D138

Press Ctrl-X when done to save

CTRL-x

Deploy Dependancies

appimage-builder --skip-test --skip-appimage

Test your Appimage directory

AppDir/AppRun

Build your appimage as follows

appimage-builder --skip-build --skip-test

Run your newly built app-image

SimpleQtApp-latest-x86_64.AppImage

Hope this helps anyone else struggling with this tutorial on Debian 10.5

Done.