I'm finding that InDesign is breaking Command+Tab (app switching) in Big Sur, from 11.0 to 11.1, the current version.
Quitting InDesign brings it back, and simply booting InDesign breaks it. Leaving it open in the background once broken keeps Command+Tab broken until I quit InDesign.
Anyone else? Is there the same key command hiding in the app? I went through Keyboard Shortcuts as well as Apple's Shortcuts and found nothing conflicting.
I haven't experienced that issue, yet. I'll keep my eye on it and will swing back to let you know if it does start to happen.
In the meantime, you can report it here: https://indesign.uservoice.com/
I had noticed random problems with app switching in that ID would sometimes fail to come to the foreground (menu or otherwise) when switched to. InDesign 16.0.1 Mac 10.14.6
For me it completely kills app switching; nothing happens when activating the key command.
I am running Big Sur 11.1, InDesign 6.0.1 on a MacBook Air.
I have no problem switching applications with Command + Tab.
You might try restoring your InDesign preferences for troubleshooting purposes: