Less language is an extension of css and less4j compiles it into regular css. Less adds several dynamic features into css: variables, expressions, nested rules, and so on. Less was designed to be compatible with css and any correct css file is also correct less file.
Specifically do you know if this LESS update is included in the current version of less4j?
If you are using the semantic-ui-less package with versions of LESS before 3.5 some calc values will not be computed correctly due to changes in variable interpolation. It is recommended that you upgrade to at least 3.5 to continue using new versions of SUI.
Specifically do you know if this LESS update is included in the current version of less4j?
https://github.com/Semantic-Org/Semantic-UI/blob/master/RELEASE-NOTES.md#version-241---oct-13-2018