Sorry for replying to an old thread, but just to add if someone is looking to install LL on a ChromeOS machine, especially if Google has stopped updating it. I installed LL 5.8 on an old Dell Chromebox that had Mr Chromebox's UEFI firmware installed, replacing GalliumOS now with LL 5.8. I changed out the original 16GB M.2 drive for a 128GB M.2 and installed LL 5.8 and everything is humming along quite nicely.
So for me and this old Dell, 5.8 works just fine with UEFI and switching out M.2 drives makes a sweet little HTPC/media client.