Decorations appearing in GTK apps

Hi all, since friday's update, some GTK apps (not flatpaks, from the repo) started showing an extra decoration. Anyone facing this too? Solutions?

Oh, I see it too, also with flatpak apps like Sound Recorder 42.0

looks like there is no way to switch to the dark theme atm
looks like there is no way to apply plata-noir theme because 42 is not supported (moreover plata-noir 4.x is not in the flathub repo)

org.gtk.Gtk3theme.Plata-Noir 3.22
org.gtk.Gtk3theme.Plata-Noir-Compact 3.22

PS: love that lovely quote in your Weather app 🙂