Biggest UX challenge with Signal for a normal person is the backup and recovery step. Whatsapp has made the process so seamless and Signal by design just cannot do it.
https://support.signal.org/hc/en-us/articles/360007059752-Ba...
Imagine you lost/broken phone and bought a replacement. Whatsapp would be able to restore all your history while in Signal you are out of luck.
> How do I enable a backup? Can I use an iCloud backup?
>
> - Storing messages outside of your active Signal device is not supported.
> - Messages are only stored locally.
> - An iTunes or iCloud backup does not contain any of your Signal message history.