Ask HN: What's with the DIY state of the art long-range Wi-Fi?

The Pi is lousy for that unless you get something with an external antenna connector. Back in the 2000s, we set up inter-building links with Cisco Aironet PCMCIA cards (which did not have the EIRP power limits currently enforced for consumer products) at blistering 11Mbps speeds (well, it was fast for the time) and a few years later we did it again at 54Mbps in the 2.4GHz band with OpenWRT devices like the WRT54g, doing 10Km with external directional antennae.

I also built my own 3G range extender with an almost identical off-the-shelf $50 Yagi antenna at a country cottage (2.2 and 2.4GHz are close enough for an antenna to carry both), so I've spent a while pondering those kinds of scenarios.

But addressing your points directly, I would look for OpenWRT-compatible devices with external antenna ports and the ability to do both 2.4 and 5GHz - and most likely try to use 2.4 for long-distance point-to-point links with Yagi antennas.

Hitting the bitrates you mention seems perfectly doable, although I must point out that the antennas are conspicuous (about the length of two Pringles cans). The challenge I found is having router hardware that can pin SSIDs to separate radios, because most of the modern stuff aims for diversity and prioritizes throughput.

There is HamWAN (https://hamwan.org/) that works over amateur radio frequencies. Seems like a very DIY, volunteer, and helpful community

The state of the art for any non-ionospheric relatively high frequency radio transmission is how high the antenna pair are above their local terrain. Power input, modulation, antenna type, these hardly matter in the face of a hill or a valley.

The only thing that matters for 2.4/5 GHz wifi long range is height above surrounding terrain to get line of sight. The highest technology is literally the technology to get the antennas highest; ie poles, towers, tops of tall buildings, actively lifted (and powered) drone platforms for antennas, sides of mountains, etc.

This is the right answer. The Freifunk people have a lot of experience and knowledge.

Anecdote: A while back I was moving houses ~1km with trees obstructing line-of-sight and without connectivity at the new house for the first couple of months. I had to move but could keep the old place connected. I jerry-rigged Ubiqity PtPs that I had inherited from a friend at each end. Packets started dropping on rainy days but it was working surprisingly well.

Not necessarily a fan of Ubiquity and their closed ecosystem per se, and it might not be the best pick for a project like OPs if there are options.

(Throwaway because these hotspots were brought from abroad..)

My time to shine- this is for anyone concerned about ham operation in Ukraine

https://eindhoven.space/2022/10/08/ham-radio-usage-in-ukrain...