Suggestion (Required)

Issue was recently fixed according to the changelogs here:
https://www.curseforge.com/minecraft/mc-mods/servercore/files/5230932
https://www.curseforge.com/minecraft/mc-mods/servercore/files/5230942

In case it helps to move this along, I can confirm that its resolved (servercore doesn't use nightconfig anymore).
The game can load fine with both mods installed using this fabric_loader_dependencies.json on fabric;

{
  "version": 1,
  "overrides": {
    "nightconfigfixes": {
      "-breaks": {
        "servercore": "IGNORED"
      }
    }
  }
}

Ofcourse this isn't actually a solution though, so it would be nice if this breaks clause could be changed in night-config-fixes.