[Bug] [Flatpak]: "System Default" base theme does not switch to or from dark mode

[ghost]

Guidelines

• I have encountered this bug in the latest release of FreeTube.
• I have encountered this bug in the official downloads of FreeTube.
• I have searched the issue tracker for open and closed issues that are similar to the bug report I want to file, without success.
• I have searched the documentation for information that matches the description of the bug I want to file, without success.
• This issue contains only one bug.

Describe the bug

When switching to light or dark theme on system, freetube does not follow that setting, and has to be manually switched.

Expected Behavior

FreeTube's theme should automatically switch to light or dark theme, based on the system prefrences

Issue Labels

visual bug

FreeTube Version

v0.19.0 Beta

Operating System Version

Fedora Workstation 38

Installation Method

Flathub

Primary API used

Invidious API

Last Known Working FreeTube Version (If Any)

v0.19.0 Beta

Additional Information

This feature worked previously on Debian GNU/Linux 12.

I also tried re-installing all the necessary xdg portals, and granting FreeTube additional permissions through Flatseal.

Nightly Build

• I have encountered this bug in the latest nightly build.

[efb4f5ff-1298-471a-8973-3d47447115dc]

This is a duplicate of #2831