I have UniElec U7621-06 and I'm using my old WN722N usb wireless adapter as wireless AP device.
I want to buy a newer OpenWRT/LEDE supported 5ghz usb wireless adapter.
Which one should I buy?
What about this one?
https://wikidevi.com/wiki/EDUP_EP-AC1621 says it has Realtek RTL8814AU chipset
Unless things have changed in the last few months there are no USB 802.11ac devices that work under Lede. You might be able to get one working, but it won’t work with the web interface and will require compiling your own driver.
I’m holding out hope that the atheros USB ones will be supported soon, as USB is getting added to the mainline ath10k stuff.
While I haven't yet had success finding a USB WiFi adapter that meets my requirements of 802.11ac, 802.11s, monitor, and multiple modes (ideally AP, STA, and mesh), I have a few resources that may be of interest.
https://wireless.wiki.kernel.org/en/users/drivers -- a view into level of support in Linux drivers
Also, from about a year ago:
which also gives links to get lists of devices with specific chips, at least for the revision examined, for AR9271, for example. That post also points out that
the TL-WN822N USB wireless adapter by TP-LINK comes with 3 versions. The version 1 uses two different chipsets, which is Atheros AR9170 and AR9102 while version 2 has the Atheros AR7010 and AR9287 chipsets, and the latest version 3 uses Realtek RTL8192CU.
Similarly, the TL-WN822N[C] now has a v2 that uses a Realtek RTL8188EUS, according to https://wikidevi.com/wiki/TP-LINK_TL-WN722N