How to root Samsung S6 using Linux?
There is a cross-platform version of Odin called JOdin. It can run in a web browser, or locally after downloading the JAR file. Either one requires Oracle Java 8 to be installed first.

Web version: https://builds.casual-dev.com/jodin3/
Offline version: https://builds.casual-dev.com/index.php?dir=JOdin3%2F  '

The offline version is started with $ java -jar /path/to/JAR/JOdin3CASUAL-r1035-dist.jar.

Both versions work well - but now I run into the next problem which is that the PIT file can't be obtained.