I received an Adalm Pluto today from Digikey which is revision D.  This revision has clock in and out connectors and also RX2/TX2 wired out.  All four ports are provided through u.fl sockets on the pcb.

Details from from Analog Devices below

Image - https://wiki.analog.com/_media/university/tools/pluto/hacking/pluto_c.png
Mine has 3.3V max silked screened next to the clock input.

Wiki - https://wiki.analog.com/university/tools/pluto/hacking/hardware#revision_d

73 de Mark, G6DDX