I found this 2 years old post at Ubuntu Forum:
https://ubuntuforums.org/showthread.php?t=2407207
The last posting might help you:
On doing some research, found out that this issue is specific to Fujitsu laptops, not sure why - but there are some threads where people faced similar issues for Fujitsu laptops dated long back in 2012 too. On Fujitsu laptop Ubuntu install somehow play with BIOS and alters it so that default BIOS screen is not shown and makes the user stuck on that screen with only option of "ubuntu", which too does not work.
See links below to similar issues reported earlier:
Bug filed on Ubuntu in 2015: https://bugs.launchpad.net/ubuntu/+s...x/+bug/1451387
Someone reported in 2014 13.04 laptop with EFI but cannot enter BIOS -- this thread saved my life. I followed instructions in this to reset the BIOS to factory settings by shorting-circuiting the pins on motherboard. After doing that when I started the laptop and it directly booted Ubuntu. Thank god I found that thread




The shipping cost was also covered by the manufacturer.

You are doing a great service for anyone who will find this thread in future!
That is why I prefer using VM Windows protected within Linux.