I am attempting to use ange-ftp in emacs 26.2 with lftp 4.8.4.

lftp as a standalone client is fine. Inside an emacs terminal it is
operational, too.

However, upon executing

    emacs /ftp:anonymous@slackware.cs.utah.edu:/slackware/

from a console or xterm or invoking C-x C-f ...,

the emacs messages buffer displays

"Loading ange-ftp...done
For information about GNU Emacs and the GNU system, type C-h C-a.
Opening FTP connection to slackware.cs.utah.edu...
tramp-file-name-handler: FTP Error: OPEN request failed: LFTP | Version
4.8.4 | Copyright (c) 1996-2017 Alexander V. Lukyanov"

Here's the relevant entries in some key files

init.el
  (load "ange-ftp") ;;redundant?
  (require 'ange-ftp)
  (setq ange-ftp-default-user "anonymous")
  (setq ange-ftp-generate-anonymous-password t)
  (setq ange-ftp-ftp-program-name "lftp")
  (setq ange-ftp-ftp-program-args '("-v"))

~/.netrc
  default login anonymous password none

I have tried numerous variations of parameters plus other hosts with no
success. TRAMP with SSH is working, though.

Any clues to resolving this issue would be appreciated.

Thank you.

Guido