Feature Request: Mobile as a relay for Desktop only usage

[rmlibre]

Please add the option to disable syncing desktop keys with a mobile device. This would allow users to set up trusted FLOSS operating systems to run Signal, and not have to share plaintext messages with closed source and untrustable mobile phones.

This would make Signal Desktop a more secure communication option for people who can't trust their phones to not spy on them.

**EDIT: Importantly, this option should only be available from a desktop client, ensuring control over toggling this feature stays on the trusted platform.

[stale]

This issue has been automatically marked as stale because it has not had recent activity. It will be closed if no further activity occurs. Thank you for your contributions.