Linux. Please note that your other alternatives include: building JtR from
source on your own (easy and generally recommended to do on Linux), purchasing
JtR Pro, using the "john" package provided by your Linux distribution (many
do, including Fedora, RHEL/CentOS, Debian, Ubuntu, Gentoo, and others - and
indeed Openwall), or using the Ubuntu snap package. The functionality,
performance, and dependencies of different builds of JtR may differ (due to
patches, build options, and build systems). See also:
https://www.openwall.com/john/pro/linux/
https://openwall.info/wiki/john/custom-builds#Compiled-for-Linux-x86
Ubuntu snap package:
https://snapcraft.io/john-the-ripper
https://github.com/claudioandre-br/packages/blob/master/john-the-ripper/readme.md
All of the user-contributed builds that existed in this directory have since
become obsolete and have been moved to the historical/ subdirectory.