EnableSingleFileAnalyzer is not supported for the target framework. Consider multi-targeting to a supported framework to enable single-file analysis, and set EnableSingleFileAnalyzer only for the supported frameworks. For example:

<EnableSingleFileAnalyzer Condition="$([MSBuild]::IsTargetFrameworkCompatible('$(TargetFramework)', 'net6.0'))">true</EnableSingleFileAnalyzer>

EnableSingleFileAnalyzer is not supported for the target framework. Consider multi-targeting to a supported framework to enable single-file analysis, and set EnableSingleFileAnalyzer only for the supported frameworks. For example: