Is it possible to add 5GHz wifi capability to a Samsung A3 2016 through a dongle? Question in title.

I have a drone I need to test which requires a 5GHz connection.

If it's possible to add 5GHz wifi capability through a dongle then I want to give it a go.
No. It's not possible

Your device doesn't support dual band (802.11 a or ac not supported) and adding OTG dongle that supports dual band isn't going to help. As an analogy, your service provider may provide WiFi but if your router ( like the older ones) doesn't support 5Ghz you can't use it in upper band