If it's any help to anyone, I had basically the same problem with my LG V20, which, apparently, is notorious for losing its WiFi connection. Infuriatingly, it was an intermittent fault. Don'tcha just love those? It would disconnect randomly and for no apparent reason. Sometimes it would go weeks without a problem, and then start playing up again. The past few days, however, it got really bad and couldn't stay connected to my home wifi for more than a minute or two. I had to keep putting it in aeroplane mode for a second or two, and then it would invariably re-connect. Like the OP, I scoured the forums for weeks looking for a solution, and I tried most of them - including a (highly inconvenient) factory reset. That seemed to work, too, but only for a week or two.
Finally, having noted by this time that it didn't seem to happen at other locations, I started thinking about the (dual band) Hauwai router I was given by my ISP and wondering if that might be the source of this problem that was by now driving me nuts. So I logged into my router's settings on my laptop and simply switched off the 5 Ghz signal to see if it would make any difference. Since then, the connection has been perfect. Two days later, it's gone from disconnecting practically every minute to remaining connected constantly. I don't claim to know why this has happened, or why the phone apparently couldn't handle the 5Ghz band running alongside the 2.4 Ghz one, but frankly I don't care. The important thing is it's working. Hope this helps someone else, too.
