Have you looked at shielded twisted pair or optical fiber for that run? I have a similar project planned but at the moment I’m not looking forward to trenching the cable into the ground so it hasn’t moved forward yet.
I need it to be able to deliver PoE, which is why I went for Ethernet - but yeah, probably going to replace it with STP, although not sure that’s going to stop lightning induction in the earth/shielding. Other option is splashing out for SWA STP, which should definitely do the job.
For the other run, where I don’t need power, I’m using 802.11n with a pair of Yagis to go about a kilometre. No problems except the usual headaches around layers and discovery a Wi-Fi bridge provides.