Ubuntu – Ubuntu is a boot option, but it’s not in the boot order setup

I've had a Windows 10 and Ubuntu 18.04 dual boot for a year. Both OSs work fine. My computer loads Windows by default on start-up, but I'd prefer on start-up to select either OS from the GRUB boot menu option or start Ubuntu at least. I went into the boot menu where Ubuntu is listed and then into the boot order setup, but in the boot order Ubuntu was not listed (see images).

Did I install Ubuntu wrong or is it because I have both Windows and Ubuntu on SSDPEKKW512GB (see images). I don't understand sysadmin and hardware stuff.

Is there a workaround that lets me have on start-up the boot screen or that loads straight into Ubuntu?

Sometimes I need multiple restarts followed by pressing Fn+F7 to get into the boot screen. Somehow they get ignored and Windows starts straightaway. Is this connected to the previous issues?

This thread doesn't solve my issue, I have already tried GRUB_DEFAULT=0 and Ubuntu in the /etc/default/grub file without success.

Just in case I attached my grub screen too.