Like I said, there are some I2C LCDs that accept change of address.
For ordinary serial LCD, you may do two software serial ports each controlling one LCD.
By default, you can't connect multiple serial LCDs to one serial port and expect them to know which one is addressed. You need firmware support. I design and sell my phi-panel serial LCD backpack, which has firmware to support addressing up to 255 LCDs on one serial port. You start with enabling addressing on the LCDs and then declare which LCD to address and print to it.