> The SFP+s use the same SC connector used in PON networks, but otherwise use Active Ethernet. I’m not sure if they’re using IEEE standards or are proprietary on the glass, but I’ll assume the latter.

It's actually standards compliant (unless they screwed something up). IEEE 802.3 clause 158: 10GBase-BRx, where x = 20 in this case, at least the ones on the Amazon link say 20km. The 1G/2G support is "bonus" beyond the spec.

You can get them with LC connectors too, which I'd in fact recommend because those are smaller, a bit more precise, and waaaaaay more common these days. https://www.fs.com/eu-en/products/36351.html (note you need a pair of "23" and "32")