Getting Started asked to flash SD card using escher but that software is x86 only.
For those of us using a arm64 Linux system, I might suggest the standard dd utility.
sudo dd if=XXXX.img of=/dev/sdX bs=4M status=progress conv=sync
Plugging in a flash drive and looking at dmesg | head -30 (30 lines of output) usually shows the /dev/sd used (e.g. /dev/sda, /dev/sdb, …).
HTH
-KenD