inetutils-telnet(1) on Linux
The text 8de89551308b, as Debian 9 (Stretch) shipped it.
user interface to the TELNET protocol
Flags it lists
-
-8 -
-E -
-F -
-K -
-L -
-S -
-X -
-a -
-c -
-d -
-f -
-input -
-k -
-l -
-n -
-output -
-r -
-x