A recent windows or acer bios update caused my laptop to always boot windows and not my usual dual boot grub ubuntu linux menu. I found that booting while holding F2 brought up the bios menu and navigating to the boot section, I saw that Windows Boot Manager was selected as the first option in the boot sequence. I moved Window Boot Manager down below the HDD option using F5/F6 then exit bios saving changes. I found that it immediately restored my dual boot menu so I could choose my usual ubuntu.
Phew!
