As per the documentation: ⌘+`

I'm using Opera One(version: 114.0.5282.185) (arm64).

Note that this is in the "Opera for Mac" category.

I also see that this bug was first reported in the community forums in 2021, and it has not been responded to nor resolved since then.

"Cycle through open windows" keyboard shortcut doesn't work with the default shortcut, and the settings page doesn't allow rebinding it to another keyboard shortcut.

Documentation should be updated to remove this keyboard shortcut because it doesn't work and it's no longer available under settings.