Hi @JAY_SUN1
There's no demo project for S32K328 derivative. You can use any S32K3x4 project as a starting point. In fact, all S32K3x4 are almost identical devices, there's just different configuration of cores (S32K314 - single core, S32K324 - dual core, S32K344 - lockstep). Because S32K328 is dual core, it makes sense to use S32K324 demo.
Please notice that Unified bootloader is unofficial reference code only shared on the community, it is provided AS IS with no guarantees and with limited support.
Regards,
Lukas