Trying to install Gentoo Linux, stuck at GRUB

I am trying to install Gentoo Linux, following the instructions on their website, but I cannot go beyond a GRUB prompt.

I downloaded the "Minimal Installation CD" ISO, AMD64, 2019.04.21, and burned the ISO on a FAT32 formatted USB stick with Unetbootin 661. The system is set to boot in UEFI only, secure boot is disabled, and the USB port has the priority in booting.

According to Gentoo documentation: "A boot prompt should be shown. At this screen, Enter will begin the boot process with the default boot options. To boot the installation media with custom boot options, specify a kernel followed by boot options and then hit Enter."

All I get to is a GRUB prompt. Pressing Enter I just go on a new line. Pressing TAB I have a list of the available commands, but I cannot launch the boot nor specify the kernel version.

The system is a Lenovo ThinkPad E585 (2018), with AMD Ryzen 7, and BIOS updated to 2019.04.09.

I recently ran into this issue. I'm 99% positive that you were trying to boot via UEFI, which the minimal installation media does not support, see https://forums.gentoo.org/viewtopic-t-1050124-start-0.html.

I would recommend using a system rescue cd, or just simply install using another distro's live cd.