Load external presets from plug-in running in a sandboxed DAW (Flatpak, Linux)

I try to help AudioThing debug an issue where all of their plugins can’t access any of the presets stored in:
~/.local/share/AudioThing

My motivation is to make plug-ins work in Flatpak - one of the most widely used distribution channels for apps on Linux.

Out of over 200 plug-ins that I actively use, the AudioThing plug-ins are some of the few that have problems with a Flatpak DAW.

Since AudioThing can’t to invest time in debugging this problem, I thought I’d ask you guys here if anyone might be able to give me a hint on how AudioThing could this problem.

Steps to reproduce

  1. Open a Flatpak DAW such as Bitwig Studio or Ardour (those are the ones I tested)
  2. Insert any AudioThing plug-in (it doesn’t matter if you use VST2, VST3 or CLAP as they seem to behave all just the same)
  3. A. Try to select a preset by clicking in the preset selector or on any of the up/down arrows
  4. B. Click on the “Open presets folder…” button

Expected behavior

  • A: Ability to select (and load) presets
  • B: Open the presets folder with the system’s file browser (in my case nautilus on GNOME)

Outcome (bug)

  • A: None of the presets show up and or can be selected/loaded
  • B: Clicking on the “Open presets folder…” button has no effect

Note

  • I did grant the DAWs specific access to ~/.local/share/AudioThing/ and also tried to allow all files, nothing had an effect
  • I tried to run the DAWs with flatpak run -vto see if there were any debug statements posted, unfortunately there were none
  • I made some screen grabs that can be downloaded here: Internxt Send - Securely Send Large Files for Free

Test system

  • Computer: Lenovo ThinkPad Z16 AMD Gen1
  • OS: Manjaro Linux x86_64
  • Kernel: 6.5.13-7-MANJARO
  • CPU: AMD Ryzen 5 PRO 6650H with Radeon Graphics (12) @ 4.564GHz
  • GPU: AMD ATI Radeon 680M
  • Memory: 9086MiB / 15253MiB
  • DAW: Bitwig Studio 5.1.6 (Flatpak)