LINE - just the tip of the iceberg of privacy and security concerns. https://reports.exodus-privacy.eu.org/en/reports/jp.naver.line.android/latest/

Agreed. May best to get family and close friends on Signal right away. Telegram is horribly unsecure.

Signal desktop is designed to be a stand alone app that uses the phone phone to first verify the connection via QR but after that relays messages, calls, erc direct from and to the server, inrependently of the phone app.