So I think it actually IS an Ethernet cable.
Looking farther into the hole on the cable markings, I see "ETL VERIFIED TO TIA/EIA 568B."
However, I think I don't know where the cable comes out on the other side. The ones in the "structural panel" that are yellow are all rated CM and this one is CMR, so I don't think it is the same cable.
Since it has moving parts I would place it up top, where it will be (slightly) more protected from the elements and grime, presumably in the shadow of the bannister/rail. That's not a huge reason, but it is a reason. If it looked like a robot factory in an otherwise pretty spot, that would probably rule out that placement for me.
That is a Homac 600V rated splice so it's probably part of your electric service. I would be calling the power company right now and report a dig in to an exposed service or secondary lateral.
Stay away from it until the power company inspects it. It could be an abandoned line but you want to assume it's hot. It looks like a ground rod has been driven close ...