I don't like the "join" button does. I prefer to configure manually. Go to wifi and create a client interface with the SSID and encryption matching the AP you want to use. Attach it to the 'wan' network, which exists by default even in a single Ethernet port device. Be sure the overall wifi radio enable is enabled. Then go to network interfaces wan physical settings and uncheck the bridge box and make your wifi client the only thing in wan. A regular AP-client link will not work in a bridge.
If you are in range of the AP the main status page should show a WAN IP address has been obtained. If this address is in the 192.168.1.X range you will need to change the LAN from the default of 192.168.1.1 to something in another range like 192.168.2.1.
This configuration is called a "routed client". The router gives you your own LAN. The AP you connected to is used as the link to the Internet instead of a wired modem.
(Last edited by mk24 on 19 Jan 2018, 23:04)