After github.com crypto update here, jgitflow is not working anymore using git:// (ssh). There is only one workaround to rely on, via https protocol. (TLS 1.2). Let's agreed that if nobody take care of this issue, this project must be considered as un-supported.
The -X flag show the issue in jsch, It should be nice if someone update to 1.54 to see if that should fix the pb.
I totally can recommend it. The plugin behaviors is a little bit different but the change is pretty smooth.
this is now affecting Bitbucket since 12/1. This project needs to be updated or marked as unsupported. It is now no longer working with the 2 major hosted SCM providers.
if there a alternative plugin?
depends what you mean by alternative. Yes there is another plugin but it does not provide some of the necessary options that we make use of.