The modification user manual shows various options, but it is not clear to me what the minimum requirements are.

For minimal 4G – 1x 2×2 MIMO antenna connected into the 2x 4G low band connections.

For minimal  5G- 2x 2×2 MIMO antennas 1x antenna connected into the 2x 4G low band connections and 1x antenna connected into the 2x 5G connections.

For full performance – 3x 2×2 MIMO antennas 1x antenna connected into the 2x 4G low band connections, 1x antenna connected into the 2x 4G high band connections and 1x antenna connected into the 2x 5G connections.