Ruby gems use a slight variation on the Semantic Versioning specification. In Semantic Versioning, the pre-release specifier is provided after the dash (-). However, for Ruby gems, the platform and OS are placed after the dash and pre-releases are specified by using non-numerical characters in the version's core components.

For example, 2.0.0.a is the pre-release version a of the 2.0.0 version.

The particular issue I am running into is that nokogiri version 1.18.9-x86_64-linux-gnu is being treated as less-than 1.18.9. However, the -x86_64-linux-gnu string is not part of version string and should be ignored for version comparison.

Source: https://guides.rubygems.org/patterns/#semantic-versioning

Note: I am not a Ruby expert. I am just using jekyll to build docs. While I believe what I wrote is accurate, it would be good to double check.