in.telnetd(8) on Linux
The text 3e23fb4ff5f2, as Debian 11 (Bullseye), Debian 9 (Stretch) shipped it.
DARPA telnet protocol server
Flags it lists
-
-D -
-L -
-N -
-S -
-X -
-a -
-edebug -
-h -
-n -
-s -
-z