As you said the S32K144 has 3x LPUART. If you need more you can configure FlexIO as UART.
FlexIO has available 4 Timers, 4 Shifters, 8 Pins
For one UART 2 shift registers and 2 timers are needed.
For example, if you look at pins PTD1 and PTD0 you can see that these pins are not multiplexed to LPUART. So, you can use it in the FlexIO function as TX and RX.
I hope it helps.