Why do GTK(4) Flatpak applications have incorrect font AA?

[rokejulianlockhart (Mr. Beedell, Roke Julian Lockhart)]

Font Configuration

The undermentioned screenshot of kcm_fonts demonstrates how it should be, both in how the screenshot depicts it rendered, and what the depicted configurations demonstrate:

Examples

1. Czkawka

   This is not adhered to by the GTK4, ^[1] presumably non-libadwaita, ^[2] Czkwaka:

   

   #!/usr/bin/env -S bash
   flatpak info 'com.github.qarmin.czkawka'
   

             ID: com.github.qarmin.czkawka
            Ref: app/com.github.qarmin.czkawka/x86_64/stable
           Arch: x86_64
         Branch: stable
        Version: 8.0.0
        License: MIT
         Origin: flathub
     Collection: org.flathub.Stable
   Installation: system
      Installed: 25.4 MB
        Runtime: org.gnome.Platform/x86_64/47
            Sdk: org.gnome.Sdk/x86_64/47
   
         Commit: 8f3052d3cdd7186f7ab6b693066bb730d047e7ddaff9a127754b6e1a134e8167
         Parent: eac69a7ec3837f2acbb85290c6ed60054a33f9761e02f5f522bad107acdcfaa5
        Subject: update to 8.0.0, bump runtime and dependencies (#26) (2740a58f)
           Date: 2024-10-11 07:53:47 +0000
   

2. Planify

   Additionally, not even libadwaita saves Planify:

   

   #!/usr/bin/env -S bash
   flatpak info 'io.github.alainm23.planify'
   

             ID: io.github.alainm23.planify
            Ref: app/io.github.alainm23.planify/x86_64/stable
           Arch: x86_64
         Branch: stable
        Version: 4.11.6
        License: GPL-3.0+
         Origin: flathub
     Collection: org.flathub.Stable
   Installation: system
      Installed: 35.0 MB
        Runtime: org.gnome.Platform/x86_64/47
            Sdk: org.gnome.Sdk/x86_64/47
   
         Commit: 609cfc539fe4765000cb67c9d767d7cac76642a4b6218fe67ecda83a413bd6f8
         Parent: 19ef3fd7a1cb5d34bc24e03a7da513bbb092690fddde247db0ccb2f3dde5d89f
        Subject: Update io.github.alainm23.planify.json (4223ca7d)
           Date: 2024-11-05 05:30:23 +0000
   

Why is this, and (how) can it be remediated?

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