I ran dmesg before connecting the TL-WN722N and then ran dmesg after connecting the TL-WN722N (and waiting 2 minutes) to look for the differences, then disconnect the TL-WN722N again and waited for 2 minutes. See the results below:
[ 1292.723817] usb 1-1: new high-speed USB device number 2 using ehci-platform
[ 1466.883137] usb 1-1: USB disconnect, device number 2
According to wikidevi the TL-WN722N is using an Atheros AR9002U chipset so i made sure i have the drivers for that installed too, as the package below:
The original TL-WN722N was using kmod-ath9k-htc (not kmod-ath9k), but I doubt you can still buy those. For the intermediate version you probably need rt2x00, for the more current ones some kind of Realtek driver.
It's probably easier to check it on a normal desktop system running a recent linux distribution.
//The joys of changing the underlying hardware while keeping the same product name/ number
Just remember that after any firmware upgrade you will need to install those drivers again as frustratingly LEDE doesn't do it for you. (or at least it didn't the last time I upgraded)
I fell into that trap before when upgrading remotely and the USB dongle was the uplink, oops.