"Windows Boot Manager" is the only option in my BIOS.

Hello Daniel,

This is an issue with Acer itself. In order to create the Boot Choice menu, please follow these steps:

Completely shut down your computer.

Power on the system. As soon as the first logo screen appears, immediately press F2 to enter the BIOS.

Use the right arrow key to select Security.

Use the down arrow key to highlight Set Supervisor Password and press Enter.

Create a password and press Enter. Retype the password to confirm and press Enter again.

Use the right arrow key to select Boot.

Press the down arrow key to select Secure Boot and press Enter.

With the arrow key, highlight Disabled and press Enter.

Press the F10 key and select Yes to save the changes and exit the BIOS.

NOTE:: We suggest removing the supervisor password immediately after enabling Secure Boot. If you choose not to remove your supervisor password, make sure you write it down for future use.

I had to do this with couple of Aspires, then the function key F8, F10 or F12 will bring up the Boot Choice menu. Not near the laptop and forgot which key it was.

Regards,

Edit: I think under Security did you enable Boot Choice Menu. Go through all your menu items to check. Sorry I missed you already had Secure Boot enabled.