Lol @ thread and all of these overkill solutions
I would just get a power line kit and WiFi extender
LOL "Overkill solutions" and then suggesting a power line kit "
AND" wifi extender? Using two solutions when potentially one or the other will do is not overkill?
@minstreless - Inside the main home, what is the closest to the garage you have Ethernet?
Also, you said in post #16 that because it gets "utterly cold" in the winter, running a cable is not an option. Why? Exterior grade CAT 6 Ethernet cable is designed for outdoor use. Depending on type, it is totally waterproof and designed to be buried. Other types are designed to withstand direct sunlight. Some can be buried and resist UV exposure. It still meets Ethernet requirements so it still has a functional maximum working length of 100M (~328 feet) before performance degrades. But your garage is only 6 meters away.
There are several MIL-SPEC (military grade) Ethernet cables (and MIL-SPEC connectors) designed for weatherproof scenarios and long exposure to direct sun in all sorts of extreme temperatures (-55°C to 200°C) and harsh environments.
I would recommend burying the cable rather than using a drop or hanging it. This will minimize exposure to the sun but also the constant flexing that would be imposed by the wind. Metal fatigue would eventually damage the cable.
Note sure the availability in your country but I see on Amazon here there are many CAT6 Waterproof Outdoor Direct Burial UV Resistant Ethernet cables in lengths up to 500 feet for less than $100 USD.
Yes, more work initially, but a much more permanent (meaning "one-time") project. It should be buried below the frost line, however.
Other than that, I still think a directional wifi antenna would be worth a try. In looking at the graphic for the OPs home and garage, and assuming north is "up", a directional antenna (as mentioned in Post #30) in the southwest corner of the garage pointing at the router would minimize the number of barriers the signal would need to travel through.