Google remains committed to improving device longevity
Don’t throw away your out-of-date Chromebook just yet as newly found evidence suggests Google may expand the availability of ChromeOS Flex to the old laptops.
The advantage seems to be that you would not need to reflash the bios. For some models getting to the screw is not as easy and the cable needed to unlock other models is not being sold anymore.
I tried putting Linux on an old Chromebook once and it became unusable. Probably my own fault but I'm very reluctant to try again. If Google released something then I'd feel more confident in the process.