Keyboard case is slick

[biketool]

You could also use something like Sugru to add non-slip areas and corner bumpers.

With careful measurements a .stl file for 3D printing would be pretty easy, then post the required files and either print it yourself or send the .stl to a print as a service place.  I assume a good % of users of pinephone vs normal phones have access to this tech?
Once people have one or two designs to ruggedize the Pinephone/KB cover we can start discussions of the survival of the fittest and it seems that Pine64 has experience managing a supply chain including injection molded plastics so it would probably become a store item vs DIY printing.

For 3D modelling purposes a very accurate 3D model would make subtracting that shape from a ruggedized case prototupe design becomes easy.