Which Daughterboard is suitable for expanding Encoders and I/O of a 7i96S?

Yes, I showed a NPN scheme

For a PNP scheme and  with all errors combined
you would wire the alarm outputs in series:

+24V --> ALM0+ 
ALM0- --> ALM1+
ALM1- --> ALM2+
ALM2- --> ALM3+
ALM3- --> 7I96S input

Note: with this wiring you need to be very careful that you
do not accidentally ground any of the ALM pins or you will
damage the drivers. If you are concerned about this, a say 1K
ohm 1W resistor can be added in series with the +24V connection