The issue you're encountering with KernelSU integration into the LineageOS kernel for the OnePlus Nord N200 5G device seems to be related to compatibility between the latest stable tag of KernelSU and the Linux kernel 5.4.289, particularly concerning SELinux. The errors indicate redefinition of 'current_sid' and issues with structure members in the SELinux source files. This could be due to incompatibilities or changes in the kernel's SELinux implementation that the KernelSU module isn't properly accounting for. To resolve these issues, you might consider the following steps:

  1. Check KernelSU Compatibility: Verify if the latest stable tag of KernelSU is officially compatible with Linux kernel 5.4.289. It's possible that newer versions of KernelSU might have dropped support for older kernel versions.
  2. Review KernelSU Release Notes: Look at the release notes or documentation for the KernelSU version you're using. There might be specific instructions or known issues related to the kernel version you're working with.
  3. Test Older Versions: If compatibility is an issue, try integrating an older version of KernelSU that is known to work with kernel 5.4.x. This might require some backporting of changes from newer versions if they are necessary for your use case.
  4. Apply Patches: Search for any community-contributed patches that address SELinux compilation issues with the specific kernel version you're using. Sometimes, the community might have already worked on solutions for common compatibility problems.
  5. Report the Issue: If you believe the issue is a bug in KernelSU, consider reporting it to the maintainers. Provide detailed information about your setup and the errors you're encountering. This could help in improving the module for future releases.
  6. Seek Community Help: Look for discussions on forums or community channels related to KernelSU or LineageOS. Other developers might have encountered and resolved similar issues.

Remember to ensure that any changes or patches you apply are secure and well-tested to avoid introducing new issues into your kernel build.