So, I started my Ubuntu PC, installed Unetbootin, downloaded elementaryos-5.1-stable.20191202.iso, installed it successfully on a USB stick. Relaunched my PC, pressed F12. Here comes a Unetbootin screen with one choice: "Default" and a countdown to automatic boot... 10 to 0... and then starts to count again forever. I repeated the whole procedure with a second USB stick. Same result. It seem the PC does not boot from the USB stick at all. In the BIOS I set that it can launch from Legacy and UEFI both. USB UEFI BIOS Support is enabled. There are no other options that make sense. Any suggestions, my friends?