I own a Purism Librem 13v4, which uses Coreboot for its bios. Is it possible to install Clear Linux in such an environment? Is there development underway?
Hi @insomniacsunbear, welcome to the Clear Linux* forum!
Clear Linux* needs UEFI support. I have no experience with Coreboot, but according to their documentation, it should available through UefiPayloadPkg (formerly TianoCore and CorebootPayloadPkg).
However, I may be wrong and would wait for an opinion directly from the developers. 
There’s also LibreBoot