I’d recommend you follow that “fourth” quickstart and do the “host it anywhere”. Your PKI is probably all setup for “local only” not “anywhere” (which is what you really want).
for anyone coming to this thread - EXTERNAL_DNS Is referenced in that quickstart and over here: Error creating identities instance in Ziti Edge Controller - #5 by dovholuknf
EXTERNAL_DNS is only really used to setup those other variables as shown:
Those environment variables are then used to bootstrap all your config files. Once the config files are generated, once the PKI generated, these environment variables aren’t the right thing to focus on…