This repo contains a tool for converting junitxml files to the subunit v2 protocol.
junitxml2subunit is written in Rust, so you'll need to grab a Rust installation in order to compile it. Building is easy:
$ git clone https://github.com/mtreinish/junitxml2subunit
$ cd junitxml2subunit
$ cargo build --release
Once you've built junitxml2subunit running it is straightforward. The command takes a single argument the path to the junitxml file to convert. It will then print the subunit v2 stream for that file to STDOUT. For example:
$ junitxml2subunit results.xml
Optionally there is a -o/--output flag which can be used to write the
subunit v2 stream to a file.