If your username is the same as your value of $NAME, then there will be a false positive match on your home directory in the path of the pubring file, which will make the value of $fp start with a newline, and will make the sed command fail with this error: "sed: 1: "s/pgp: FALSE_KEY_HERE/p ...": unescaped newline inside substitute pattern"
Fix it by matching on the key comment instead.

add substitute options

add note about generating entropy

rolled back to old keygen method after flux complained about not being able to decrypt using GPG key generated with --quick-generate-key, while keeping RobK's simplified imperative command