Fatih19 No, I did not find the warning, because I installed both of them with the same BIOS Mode. Both of them are currently running normally. I have to use the Boot Select menu from the BIOS to switch between Windows and Solus. I have also asked some friends who use the same brand, model, dual ssd and BIOS settings as mine. HP Elitebook 840 G2. It turns out they are with Dual OS (Windows + Debian 9), (Windows+Ubuntu 18) did not find the problem that I experienced. Do Ubuntu and Debian use Grub that already supports UEFI? I'm really sorry, I am new to Solus and UEFI things.