duplexify is used at run time in 3 crates (of which 1 optionally). It's used only as a dev dependency in 5 crates.

Depender (with downloads and own rev deps) duplexify version
smtp-client ^1.2
smtp-server ^1.1
380 7 duplex optional ^1.2.2
260 1 hypercore-protocol dev ^1.1.0
1 edelcrantz dev ^1.2.2
ssb-box-stream dev ^1.1
1 clepsydra dev ^1.2.2
gnostr-core dev ^1.1.0