The Raspberry Pi has a built-in Wi-Fi chip whose range is sometimes not enough, especially inside a metal case. To replace it with a USB Wi-Fi dongle — often fitted with a real antenna — you first have to disable the internal chip, otherwise both interfaces compete and Recalbox keeps using the built-in one.
RECALBOX partition (the only one visible under Windows) and edit the recalbox-user-config.txt file with a text editor.dtoverlay=disable-wifi
You can also edit that file over SSH: it lives in /boot, and the partition must first be remounted read-write. See also editing the boot configuration files.
After the reboot, only the USB dongle is visible: set Wi-Fi up as usual from START > NETWORK SETTINGS — see Connecting Recalbox to the network.
Check beforehand that your dongle appears in the list of compatible Wi-Fi dongles: not every model has a driver in Recalbox.
To go back to the built-in chip, simply remove the dtoverlay=disable-wifi line and reboot.
Need help? Join the Recalbox Discord.