https://github.com/AscensionGameDev/Intersect-Engine/blob/main/REQUIREMENTS.md#macos
The OS requirements for Windows and MacOS are published on the repository.
High Sierra is macOS 10.13, which is so old (3 versions before the first one listed, Big Sur) it's not on the supported OS version matrix.
Also, we are running .NET 8, which from Microsoft's documentation only supports macOS 13 and higher: https://github.com/dotnet/core/blob/main/release-notes/8.0/supported-os.md