baresip(1) on Linux
The text 8a743fe7643d, as Debian 11 (Bullseye) shipped it.
portable and modular command-line SIP user-agent
Flags it lists
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-4 -
-6 -
-? -
-d -
-e -
-f -
-h -
-m -
-n -
-p -
-s -
-t -
-u -
-v