macOS 11 (Big Sur): Graphics not visible

Test environment:

• Development beta of Mac OS X 10.16 (20A4299v) -- AKA macOS 11 (Big Sur)
• Regular "Intel-based" Mac
• Inkscape 1.0.0 release (4035a4f).

Results:

• Inkscape launches properly
• Inkscape's menu bar is visible
• Essentially, nothing else is visible.

While you can select a title from the menu, no drop-down menu items are actually visible when you click a main menu title. Rather, only the "drop shadow" outline of the menu is visible.

Similarly, the drop shadow of the main canvas window is visible, but the window itself is completely transparent. The window can be moved, but you can only tell this because the drop shadow moves.

Also note:

• The existing Inkscape install process (DMG, Gatekeeper, signing, first launch process) was flawless under Big Sur.