Install Ubuntu on AN515-55: USB boot option desn't appear

Help! I can't make the bootable USB stick appear in the boot selection menu. It has already been hours and I have tried rufus (GPT and otherwise), unetbootin (both from Linux, with gparted, and Windows). Following, multiple posts in this forum, I have also already hacked the BIOS menu and set

* secure boot off, with master password.

* fast boot off.

* SATA mode to AHCI, with all the windows safe mode shenanigans.

* F!2 boot menu to enabled.

My boot options are always invariably only:

1. Windows Boot Manager

And it is driving me insane. My system BIOS version is v1.04 and I don't know what to do anymore.

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Leostat

What USB ports does the laptop have? I have had laptops play funny with USB 3 drives, may be worth trying with a 2.0 in the 2.0 port if it has one! (I know it sounds silly)