Use gsettings:
gsettings set org.gnome.desktop.interface gtk-theme 'Adwaita-dark'
gsettings set org.gnome.desktop.interface color-scheme 'prefer-dark'
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Linux is a family of open source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991 by Linus Torvalds. Linux is typically packaged in a Linux distribution (or distro for short).
Distributions include the Linux kernel and supporting system software and libraries, many of which are provided by the GNU Project. Many Linux distributions use the word "Linux" in their name, but the Free Software Foundation uses the name GNU/Linux to emphasize the importance of GNU software, causing some controversy.
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Use gsettings:
gsettings set org.gnome.desktop.interface gtk-theme 'Adwaita-dark'
gsettings set org.gnome.desktop.interface color-scheme 'prefer-dark'
Adding
[Settings]
gtk-theme-name=Adwaita-dark
to $USER/.config/gtk-4.0
and $USER/.config/gtk-3.0
should do the trick.
https://wiki.archlinux.org/title/Uniform_look_for_Qt_and_GTK_applications
Have a look here, it might help. I can't help much, I have KDE and Hyprland but I setup theming in KDE and it also sets in Hyprland.