Clover is able to see the Ubuntu SSD as INTERNAL, but when I select to boot from it, the screen just goes purple and hangs there.
I have installed Ubuntu selecting "Something else" (prior to that used GParted to swap all the partition and create a new msdos (MBR) partition table), created a root Ext3 partition selected "/" as mount and after that I created a 12GB swap partition. Then selected to install bootloader at /dev/sda1 which is the root partition "/".
EDIT:
After some searching, I see that pressing the SHIFT key just before Ubuntu GRUB is about to load, it can popup a menu with selections. I just did that, pressed SHIFT after selected Linux INTERNAL at the Clover menu, got the GRUB menu and after the menu is displayed it hangs there. No keyboard response when I press UP and DOWN arrows nor any other key.
UPDATE:
After a lot of reinstalling and struggling, I managed to boot to Ubuntu from Clover by creating a separate boot partition and using the Boot-repair utility.
Used GParted to create a new msdos partition record.
Initially I've created 2 partitions, one for root and one for swap.
Then installed bootloader to root, was able to boot just using Ubuntu SSD, but not from Clover.
Booted from Ubuntu Live USB and followed this
guide to create a new boot partition (I can't remember exactly the GRUB options but I tried some settings).
After it's done restarted (confirmed it's booting on its own) plugged Clover SSD; Linux INTERNAL was there, selected it and finally it booted to Ubuntu!
BUT:
After some updating (I think it was just apt-get update, but maybe and upgrade I'm not sure) and restarting, selecting Linux from Clover again I got a black screen with
boot0af: error. Used Ubuntu Live USB again, start Boot Repair, rewriting the bootloader to /boot partition again and I got it working and booting again from Clover. There might be some kernel updating issue I suppose. Anyone has a clue why that happened and how can I avoid it in the future?
Anyway, I have my triple boot finally working!
Thanks again for the great tutorials!