Need help booting from USB on Dell e6410

Hello all,

For the last few days I've been trying (without success) to boot from a USB so I can install Linux on an old Dell Latitude e6410. However, the USB isn't appearing in the f12 boot menu.

I've made sure the BIOS is up to date (version A17), and have tried all combinations of BIOS settings (switching from RAID to AHCL, switching between Legacy and UEFI modes) to no end.

I'm very close to giving up. Any advice is appreciated.