A Pair of Gigabit Single Mode LC Fiber Media Converter, with 2 Pcs SFP LX Modules, 1.25G/s Fiber to Ethernet Converter, 1000Base-LX to 10/100/1000base-TX, SFP to RJ45, SMF, 1310nm, up to 20km

Oh I would do fiber, for sure. Termination (especially into 1gbit) is super cheap nowadays. (ex: https://www.amazon.com/dp/B09P8DN3HJ -> $45, everything you need but the fiber itself.) And like the other comment said, there's bound to be a pre-terminated length that's good enough. Don't forget fiber's other strength - it's non-conductive. Unless the two buildings are grounded at the same location (unlikely), there's a real chance of creating a ground loop.