Recently discovered this. Molly supports link with existing device just like on signal desktop. It even has benefit of getting entire chat history unlike signal desktop. Just restore the signal backup file during setup and then click link with existing device. Then scan with you primary phone. Beauty of open source. Molly: https://molly.im/
Also worth noting that communication between signal and matrix through most bridges requires the message to be decrypted and reencrypted, thereby breaking E2EE which kinda defeats the point.
Unless you’re running a bridge on a locked down home server on your own network, not sure it’s the most secure.
Very good point. For me its a private server and I run both the bridge and the matrix server inside the same docker network.