Some systems may require that SOM's get an external clock.
Leading a clock trace and a appropriate Gnd from the 204-connector to the SoC over an 0R-resistor would allow for this option.
For small quantities the crystal (and caps) on the standard board version could be desoldered and the 0R-resistor be soldered.
Input or output clock?
clock input
moving around 24Mhz clock signal is bad idea IMO
I do not see any benefit to clock the SOC from external source while it have on board crystal
can you please tell me what is your use case?