[newscracker]

At least Threema allows manually backing up and restoring the data on the same platform. Signal doesn't even allow backing up your conversations on iOS. Signal is coded to actively block backing up the data to iTunes or iCloud! Your chats are all gone the moment you move to a newer device (be it Android or iOS). If keeping conversations over time and having continuity is important, Signal is the last platform in this world you should be looking at.

Even Wire doesn't allow cross platform data backup and restore.

[xpaulbettsx]

That's Unfortunate, on Android you can restore your messages in Signal