This issue is blocked by #2905922: Implementation issue for Layout Builder.
Problem/Motivation
Layout Builder introduces a new paradigm shift in page building and block placement for content entities without introducing a block visibility mechanism.
Proposed resolution
Introduce a block visibility mechanism that includes individual condition configuration on a per block basis.
Remaining tasks
Upload, review and ready a block visibility patch.
User interface changes
Add a "configure visibility" link to to attached actions of a placed block within the LB user interface.
API changes
No changes, just the addition of an optional "visibility" key in the block configuration. Block configuration itself is already separated into a parallel key in preparation for this change, so the existing code anticipates this.
Data model changes
See API changes.