What can I try if a virtual-screen setup hides the login screen?

If you enabled Show on Lock Screen for a full-screen stream, try turning it off in that stream’s menu first. You can also temporarily disconnect virtual screens when the Mac locks. This can help when a virtual desktop is mirrored or streamed to a physical display and the login form is hidden behind that presentation.

Open Settings > Displays > Overview > Advanced Virtual Screen Settings… and enable Disconnect virtual screens upon lock or screen saver and connect when returning to the desktop.

The option temporarily removes virtual screens that are connected, then reconnects those screens when you return to the desktop. It keeps their saved definitions. Because their desktops disappear during the transition, applications using them can be affected. Save your work, then test locking and unlocking with your normal setup.

This is a workaround for virtual-screen presentation during a running login session. It does not establish a fix for a missing startup or FileVault unlock screen, or for a physical display that has lost its connection. See Advanced Virtual Screen Settings for related sleep and wake options.