I installed Windows 10 first.
Next, I installed Ubuntu 18 and chose "Install alongside Windows Boot Manager".
When I start my computer, it goes directly to Windows, not giving me any choice to start Ubuntu.
How can I fix this?
EDIT:
I just started reinstallation of Ubuntu to see that the current partitions on the single disk I have, as shown by the Ubuntu installation program, are:
Device Type Size Used System
/dev/nvme0n1
free space
/dev/nvme0n1p1 ntfs 554 441
/dev/nvme0n1p2 efi 104 33 Windows Boot Manager
/dev/nvme0n1p3 16 unknown
/dev/nvme0n1p4 ntfs 397782 36471
/dev/nvme0n1p5 ext4 101646 9796 Ubuntu 18.04.3 LTS (18.04)
free space 1
Figured it out right after posting this. I had to change a "UEFI priority list" in my BIOS.