@slick: the instructions we gave does not rely on any existing Arduino installation. You mentioned ‘arduino-1.8.10’: it should’t need that folder at all. If you follow the instructions it will download esp8266 core and arduino files in a self-contained folder.
Also, ~/Arduino refers to where the Arduino libraries will be installed. Since the firmware relies on several libraries, by default those libraries should be installed in that folder. If not, you can certainly modify the make file to point to the correct folder.
Also, if you still can’t get passed that compilation error, just open server.cpp, find that line and comment it out. It’s not a critical line (it basically tells the processor to stop UDP service before OTA firmware update, but that’s actually not entirely necessary).