I've had my Hubitat hub connected via LAN. I added the tp-link wifi adapter, installed the drivers and rebooted the hub - both LAN and Wifi interfaces came up on the network. I was able to bring up the interface on the Wifi network with a browser and hitting that IP address.
I shutdown the hub and moved it to a new location. After it booted up, I am able to see it from my router that it is on my Wifi network, it has the same IP address, however, when I try to navigate to the IP address it times out. When I try to discover the hub from http://findmyhub.hubitat.com/ it's not found with either the IP address or the MAC address.
What am I doing wrong?
Don't know if this is your issue, but I recently moved a hub to a TP-Link WiFI adapter and could not get the hub to connect back to the correct IP address. What I found was the TP-LINK adaptor clones the MAC address. On the adapter MAC cloning could not be turned off. I used the MAC address of my Hub to have the router set it's IP to a fixed address, since the adapter was changing the MAC, the hub would not show up on the correct IP.
Sounds like you may have a different issue since you say findmyhub won't find your hub. In my case it would it just wasn't on the IP it was supposed to be on. Mentioning the Tp-Link adapter made me think of that so I thought I would mention it.
I plugged in the LAN cable and the interface came up - both are active on my router. It has a different MAC address.
If you are indeed seeing a different MAC address for the WiFi adapter, then create a DHCP reservation for it in your router. Once that is done, try using that IP address to get to the Hubitat hub.
This is something I had to do also, I have one IP reserved with the MAC of the dongle, I had to find it in my device list on the router, happy everything on LAN has reserved addresses, makes it a lot easier to find. I also kept one IP reserved with the hubs MAC if I ever need to connect it back via Ethernet, I won't have to find it.
Did not try the hub discovery after setting it up with a WIFI connection, so not sur if that works or not via WIFI.
I replaced the hub MAC address in my router with the one set by the adapter,
but I should have set up a slot for the original MAC to make it easier to find. Although in my case, find my hub found the hub, just not where it was supposed to be.