The signal from the standard universal LNB can be split using a simple coaxial splitter (no multiswitch) to several outputs. In this case, the position, the polarization and low-high band settings must be equal.
If you set other tuner as master, then this tuner will act like a slave one and tvheadend will assure that this tuner will not use incompatible parameters (position, polarization, lo-hi).