Diffuse flatpak conffiguration file

com.github.mightycreak.Diffuse.yml

app-id: com.github.mightycreak.Diffuse
runtime: org.gnome.Platform
runtime-version: '3.36'
sdk: org.gnome.Sdk
command: diffuse
finish-args:
  - --filesystem=home
modules:
  - name: diffuse
    buildsystem: meson
    sources:
      - type: archive
        url: https://github.com/MightyCreak/diffuse/archive/add-meson.zip
        sha256: 5f68e96d825af1efbef4f9e41b92f995906919fd58e2c9de75689e47b310f826

Output of `flatpak run com.github.mightycreak.Diffuse`

Unable to init server: Could not connect: Connection refused
Unable to init server: Could not connect: Connection refused
Traceback (most recent call last):
  File "/app/bin/diffuse", line 8361, in <module>
    diff = Diffuse(rc_dir)
  File "/app/bin/diffuse", line 7375, in __init__
    Gtk.Window.__init__(self, type = Gtk.WindowType.TOPLEVEL)
  File "/usr/lib/python3.7/site-packages/gi/overrides/Gtk.py", line 521, in __init__
    "Gtk couldn't be initialized. "
RuntimeError: Gtk couldn't be initialized. Use Gtk.init_check() if you want to handle this case.