TruFont AppImage (Qt based) fails to run due to missing library

[probonopd]

#! /bin/bash

sudo apt -y install git

export VERSION=$(wget -q "https://api.github.com/repos/trufont/trufont/commits?sha=master" -O - | grep sha | head -n 1 | cut -d '"' -f 4 | head -c 7
)

export APPNAME=trufont
export PIP_REQUIREMENTS="-e git+https://github.com/trufont/trufont#egg=$APPNAME fs"
# export CONDA_PACKAGES="$APPNAME" # Only use this if the app is in a Conda channel (e.g., conda-forge)

wget -c "https://github.com/linuxdeploy/linuxdeploy/releases/download/continuous/linuxdeploy-x86_64.AppImage"
wget -c "https://raw.githubusercontent.com/TheAssassin/linuxdeploy-plugin-conda/master/linuxdeploy-plugin-conda.sh"
chmod +x linuxdeploy-x86_64.AppImage linuxdeploy-plugin-conda.sh

rm -r AppDir || true

cat > $APPNAME.desktop <<EOF
[Desktop Entry]
Version=1.0
Name=TruFont
Exec=trufont %U
Terminal=false
Type=Application
Icon=$APPNAME
Categories=Graphics;
EOF

cat > AppRun <<\EOF
#!/bin/bash
HERE="$(dirname "$(readlink -f "${0}")")"
exec "$HERE/usr/conda/bin/python" "$HERE/usr/conda/bin/trufont" "$@"
EOF
chmod +x AppRun

wget -c "https://github.com/trufont/trufont/raw/master/Lib/trufont/resources/app.png"
convert app.png -resize 512x512 $APPNAME.png

./linuxdeploy-x86_64.AppImage --appdir AppDir --plugin conda -i $APPNAME.png -d $(readlink -f "$APPNAME.desktop") --custom-apprun AppRun --output appimage

results in

me@host:~$ ./TruFont-d1ef225-x86_64.AppImage 
qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

Available platform plugins are: eglfs, linuxfb, minimal, minimalegl, offscreen, vnc, wayland-egl, wayland, wayland-xcomposite-egl, wayland-xcomposite-glx, webgl, xcb.

Aborted

on Xubuntu 18.04.4 LTS.