ESP8266 esptool for 64-bit linux

I am unable to install the board package for the firebeetle esp8266 on 64 bit linux. It appears that the 64-bit esptool refereneced in the package_firebeetle8266_index.json file isn't actually in the repo.
here's the errors:

Caused by: java.lang.Exception: Error downloading https://raw.githubusercontent.com/DFRob ... x64.tar.gz

Index error: could not find referenced tool name=mkspiffs version=0.1.2 packager=firebeetle8266