Now they all have an unlocked bios firmware and ready to take an OS.  

Most of the chromebooks are Google "Candy" (have the plastic bezel around the screen) with a 

few of Google "Wolf"  (all glass screen)  Both are 4GB ram and 16GB storage soldered in place with no upgrade.  

16GB makes Windows impossible.  And even for Linux it is hard to get a modern experience.  

Linux:  (on Candy, I haven't checked Wolf) 

You can get some of the media keys working if you change keyboard layout to "chromebook"  

(Volume works but I don't think screen backlight control works)  

Sound:  Works in full featured distros but then you run out of space in the 16GB emmc.  

Minimal distros miss some things that are needed for sound: 

Need the sound chip firmware.  On Debian it is sof-firmware so "sudo apt install sof-firmware"  

Even after installing the firmware many times the speakers are muted 

Run alsamixer from terminal ("sudo apt install alsa-utils" if alsamixer is not available) By default the Intel digital audio is selected.  F6 to change soundcard but on the chromebook the F keys are shared with the media keys.  Depends on the layout but either search (key with mag glass icon) or right ALT key is the Fn key.   Hold Fn key (search or R ALT) and press "lower backlight" (small sun icon or count 6 from ESC)  When the right sound card is selected press arrow keys until "Left speaker left dac" and press "m" to unmute then "Right speaker right dac" 

Should work now.  

Unless you have a minimal Linux distro without an audio server installed.  Then "sudo apt install pulseaudio pavucontrol" Some distros need pulseaudio-alsa (Arch) Some desktop environments may need plugins for the GUI (XFCE need xfce4-pulseaudio-plugin) 

Disk space:  This is a tough one because we have only 16GB.  There are many very small Linux distros but they are not easy for the noob or non-expert Linux user.  And if you start small and try to add you end up chasing the stuff that doesn't work.  (like Try to install wifi gui but wpa-supplicant is not automatically installed?)  You can start with something a little too big like Lubuntu then "sudo apt purge" to free space (purging Libreoffice gets Lubuntu to around 8GB)  

I will try some more distros and have some recommendations soon.  

Thomas