Yes, kirrily64. You are probably right-looks like the onboard wifi card is dead. I guess you've tried the usual things-zapping pram, resetting smc/PMU, and deleting the old wifi network, and trying to make a new one. If you go to "About this Mac" it should tell you, vaguely, if the wifi/bluetooth card is detected and working. I'd suggest going to ifixit and checking out how difficult it'd be to replace the wifi card, but that's not up to me to say. Anyways, it's not up to Apple to automatically support X or Y plugin wifi adapter . It may play nicely with Apple or not. I think you've done the correct thing in looking for one that should work with your 2010 Macbook pro with High Sierra. Edimax sez yes, it'll work with Macs running Lion on better, so you should be OK. It also mentions Mu-MIMO, but I don't know any mo' about that than you do. but apparently your router has to support it first. I don't know what kind of router you have, so I can't say if it'll do that or not. but you should for sure be able to get wifi going with this. I'd say go for it, but keep the receipt. If using this, you might want to to make a 5ghz network, and pick an unused channel for best results
good luck
John B