apt update
telling me that i386 architecture isn't supported by http://archive.neon.kde.org/user, which is weird because I've changed nothing. So I exercised my google-fu and apparently the fix in 2016 was to add /lts to /etc/apt/sources.list.d/neon.list
. Well, deb http://archive.neon.kde.org/user/lts/ bionic main
worked and updated.No doubt a new .iso will be out shortly.