Your only real option is going to be a wifi antenna then. Wifi signals are made to be short range, there isn't really anything that's going to allow you to pick it up from a distance aside from a high-gain antenna. Something like this might work
Ah, I see, if you were in a proper office building, dealing with professionals, it would be easier. I know it's 6 stories of concrete, but you might see if you can get a 2.4Ghz directional yagi to punch through, setup a WiFi bridge. Something like this has a chance, if you get two of them pointing right at each other.
Oh man. I doubt a PowerLine adapter would work.
Option 1. Run a cat5 cable. Find someway of doing it. But I can't tell if there's a good way of doing it perminantly. You could always just do a temp one everytime there's an update.
Option 2. Buy more Google WiFi. Ask to put one in that neighbor's house. While you're at it might as well ask if he wants to ditch his internet and just share a connection. If you've got like 50mbps that's more than enough for 2 houses...
Option 3. Buy two directional antenna.
Tupavco TP513 Yagi WiFi Antenna 2.4GHz 17dBi Angle H:25° V:24 Outdoor Directional Wireless https://www.amazon.com/dp/B008Z4I7WQ/ref=cm_sw_r_cp_api_i_0RkZCbVVPEWRK
And point them at each other. I don't know what to use as a bridge/repeater. All these fucking new routers have 50 antennas and all unremovable! God we've gone backwards.
You can guess at the wavelength just by the appearance of the antenna. Did it look like this, with lots of small little nubs? That's likely a high frequency antenna used around the 2.4GHz range.
Or did it look more like a traditional yagi like this or this? These are UHF and VHF antennas used for TV frequencies.
They could be either transmitting or receiving with it. Up to you if you want to knock! The good news is that whatever it is, it's almost certainly harmless. Frequencies in that range can't mess with your DNA or anything. And the cost to buy amplifiers that can make a strong enough signal where you'd actually start to worry are prohibitively expensive. Like probably worth more than their house.
Tupavco TP513 Yagi WiFi Antenna 2.4GHz (17dBi) Outdoor Directional Signal (H:25° V:24°) Long Distance Range (High-Gain Weatherproof) Wireless Network (Pole Mount) N-Female Pigtail Connector https://www.amazon.com/dp/B008Z4I7WQ/ref=cm_sw_r_cp_api_glt_i_QY9WKJGN92YXB1R7FH37
Or
https://www.makeuseof.com/tag/how-to-make-a-wifi-antenna-out-of-a-pringles-can-nb/
Yagi wifi antenna looks like
https://www.amazon.ca/dp/B008Z4I7WQ/ref=cm_sw_r_cp_awdb_t1_goFiFbH29B188
You might need a directional antenna, to be honest. And if you're looking to capture a Wi-Fi signal from a distance, something like this should do the trick: https://www.amazon.com/Tupavco-TP513-Antenna-2-4GHz-17dBi/dp/B008Z4I7WQ/
what you're looking for is two YAGI antennas pointed at each other. if you do that, you'll probably want to have the networking setup look like this. you can probably mod a wifi extender as a receiver(disable AP function), and mod the main router's wifi as the AP. i don't know what range you could get out of that though, as those devices could be lower power than needed.
Couple of options:
I got high gain Yagi antenna for WiFi. https://smile.amazon.com/gp/product/B008Z4I7WQ/ I mounted it on a camera tripod that I had laying around. To minimize signal loss I put the USB wifi device https://smile.amazon.com/gp/product/B002SZEOLG/ directly on the antenna using one of these https://smile.amazon.com/gp/product/B00F2CAFC4/. A few USB extensions allow me to place the receiving computer away from the antenna.
I can pull wifi from distant "open" hotspots as a backup to my local internet if needed. For less than $100 it is a really nice backup to have. I even set up an old netbook (Windows XP vintage) with Linux and configured it to accept the distant wireless connection and reshare it locally with a NAT firewall. https://github.com/mdeangelo001/distant_network_extender
I use one of these yagi's connected to a couple of older linksys 54G routers running dd-wrt at both sides, 1 at house and 1 at my barn/shop. They are about 1500 feet apart. I took one antennae off (at shop) and extended it outdoors with one of these http://www.amazon.com/dp/B008FH2ZBM?psc=1.
It works very well for my needs and should have enough power to blast through the few trees you have.
This setup is about 10 years old and the antennaes are new, just replaced them.