Same issue. Looks like it's the snap version of communitheme-dark.
Switched to communitheme using gnome-tweaks and got the solid-white background back, though switching back to thedark version and the transparent background is still there. Note: First, I tried Mihai Banu (m-banu94) solution and then returned to snap communitheme (not wayland) -- You received this bug notification because you are a member of Ubuntu Desktop Bugs, which is subscribed to gnome-calculator in Ubuntu. https://bugs.launchpad.net/bugs/1767541 Title: Transparent background of calculator in ubuntu 18.04 using communitheme To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/gnome-calculator/+bug/1767541/+subscriptions -- desktop-bugs mailing list desktop-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/desktop-bugs