Breakthrough Starshot Nanocraft open engineering challenges

I read about this today in Hawking’s final book. The crafts would travel immensely quickly, passing Mars in less than an hour and Pluto in a few days, and could reach Alpha Centauri in about 20 years. Importantly there can be a flyby of Proxima B, an exoplanet, which might be the first planet humans could truly colonize.

Of the two options for sustaining human civilization (AI singularity/human-computer integration and space exploration) colonizing other planets seems to me more fun and less likely to fundamentally alter/end humanity.

I’d be curious if anyone here is working on these challenges