This is the link to the thread you copied in here. I would like to answer here, because the question is more precise. There are indeed ways to add more channels/inputs, but this will never leave the 32 channel/dual-core frame of the mixers (SL 32, SL 24, SL 16, SL 32S, SL 32SX, SL 32SC). You can add more inputs via another mixer in the network and send mixes to FOH via AVB streams 33+34 (Aux In 1), 35+36 (Aux In 2) and 37+38 (Tape In/Digital Return).
This is suitable for input groups like strings or brass or choir, but not really for individual voices/singers or instruments, which probably need to be heard in monitor mixes. A 16R would add 16 input channels, which could be sent via 3 stereo mixes through the AVB network to your SL 32.
In this scenario both mixers must be connected to one router (just use a normal Ethernet switch), because you need UC Surface on a tablet (or a computer) to control the rack mixer running in Stand-Alone Mode.