Changing GTK Theme

How do I change my GTK theme?

On my Arch rig I use the Adapta theme and I used lxappearance to change it. I found both packages in nixpkgs but lxappearance is not working. Clicking “apply” in lx appearance has no effect.

I use Sway as my compositor so specific applications for particular display managers is of no help.

Thanks for your help,
Jonathan

The lxappearance package defaults to gtk2, you probably want
lxappearance-gtk3.