It’s better to find an adapter with antenna port. This is a high-powered single-band adapter  or a dual band (I’d recommend the 5Ghz band if possible, but it is still a bit rare) with RP-SMA connection . Then add a good antenna; the omni  is probably equal to the Yagi. If there isn’t interference and is dual band but this Yagi  will pull in from a longer distance. If you can get two and get a connector, you can put it “in the middle” like in a tree and point one at the source and one where you are using it, and it will be a very narrow beam. And, yes, I’ve used such. There are other adapters, antennas, and amplifiers (which I won’t go into) when I didn’t want to go through the problem of installing cable for just a few hours per day when I was home and a “main office lobby with free wifi” was available. There are various ways to get passwords for routers. Another thing is to get an inexpensive router and just “install it free” and leave it somewhere they have a few loose ethernet connections.
One thing to be careful with is some adapters can change their MAC address, which can be used as a fingerprint. (It will indicate the manufacturer, and if they try hard they might be able to trace who originally bought it.) Either randomize the MAC or buy “used” and rotate or use wifi adapters as you would “burner phones”. While the MAC is normally only known to the router, it will leave a DHCP record for hours or days on most routers. – TZ