Shortwave 2.0.1-stable not honoring gtk theme
Shortwave Version 2.0.1-stable (Flatpak) Linux Mint 19.3 Cinnamon
I have installed my system gtk theme, org.gtk.Gtk3theme.Mint-Y-Blue/x86_64, through Flatpak, so that I might have consistency of window borders across applications. Gradio, the predecessor to Shortwave, honors this, as is shown in the screenshot below. (I still had it installed, although it seems to be non-functional now.) All of the other Flatpak apps I have installed also properly honor the Mint-Y theme.
Shortwave does not use the Mint-Y theme, as shown in screenshot: