Theming Inconsistencies in GTK3 applications

[SterbenVD]

On a fresh install, when theming is applied to gtk applications via the settings:

1. No problems with GTK4 applications (both deb and flatpak)
2. GTK3 applications installed via apt get themed correctly
3. Applications such as Brave, Firefox .etc installed via apt(deb) which have the option to use the gtk theme get themed correctly only when running in wayland. When running in xwayland, it does not use the proper theming.
4. GTK3 applications installed via flatpak do not get themed correctly
5. When an flatpak application tries to launch an deb application (broswers to login for example), the now launched application does not follow the theming, even if it follows the theming when launched by the user.

System-related config:

• Have adw-gtk3 installed from deb repos
• both adw-gtk3 and adw-gtk3-dark installed in flatpak
• Using flatseal I see that globally only xdg-config/gtk-4.0 is exposed in read-only mode. Adding xdg-config/gtk-3.0 does not change the behaviour.

Possibly related to @asqwerth 's comment on #52

Edit:
Forgot to mention I tested this on a fresh popos alpha 5 iso after an apt update + upgrade.

[asqwerth]

I should have updated my earlier post. The non-theming of gtk3 apps was resolved with the alpha5 updates being pushed to the Arch repos.

I didn't test this on flatpaks, only normally built packages from Arch repos and AUR.

[SterbenVD]

I didn't test this on flatpaks, only normally built packages from Arch repos and AUR.

Yeah, the issue does not occur with system(apt) packages for me. It is just the flatpak apps.