I uninstalled Keybase from a computer. I don't know what it is good for.
The intersection of (set of people that talk to me on a regular basis) and (set of of people that are likely to use encryption), which is admittedly very small, use Signal or GPG anyway.
The filesystem is promising and could be useful.
Do you use Keybase? What do you use it for? Are you worried about lock-in? What will happen if/when Keybase runs out of money?
(They're backed by the VC firm Andreessen Horowitz.)