Can't change wallpaper in Ubunutu 20.04 Gnome Flashback

I upgraded my system (clean install) to Ubuntu 20.04. I'm not a fan of "docks," and prefer the upper and lower panels to keep track of my favorite and running apps. So I installed Gnome Flashback.

However, Variety will not change wallpapers in Gnome Flashback (it does in the default Ubuntu desktop). In fact, I'm unable to change the wallpaper at all. Tweaks shows that the correct image is selected for both lock screen and desktop backgrounds, but neither are being rendered, just the default purple background.

Any way to get wallpapers working in Gnome Flashback? Or, barring that, to be able to customize the top panel to show my favorite apps in the default Ubuntu desktop?

Thanks.