Dear Jeff,
Hello - I really have not seen you post any replies to my answers concerning your inquiries about WireGuard on your GL-AR750S. However, I was so intrigued while writing up and researching the information for your GL-AR750S that I actually went out ( read - ordered on line ) one for myself. I have been playing with it for two days - and it performs well. If you get back to me, I will write up my experiences with the GL-AR750S. So, thanks for your questions - and I look forward to our communicating as soon as you are available to do so. However, I can share with you that my instructions were correct about how to run WireGuard on this router. The only way the advice which I offered in my original answer to you does not apply is if you flashed your GL-AR750S with OpenWRT Firmware instead of the GL.iNet OEM FirmWare
From their website:
OpenWRT provides many functionalities but it may be a little too complicated for everyone. GL.iNet provides on Slate a simplified GUI with essential functionalities available. OpenWRT Luci and ( UCI command line ) are also available at the same time for advanced users. So there are two Gui's; GL.iNet Admin Gui and Luci.Do not use uci command line either. For successful WireGuard connection on the GL-AR750S - you need to configure WireGuard through the GL.iNet Admin Gui. If you set up WireGuard through the GL.iNet Admin Gui ( not Luci ) - you can SSH into your router and you can run wg show and get the same read out if you were to do a standard WireGuard install on a standard OpenWRT router. I even installed luci-app-wireguard and it shows up under Status Drop Down Menu - and it will also show you that you are connected. See here: https://danrl.com/blog/2017/luci-proto-wireguard/ When I followed this guide above that I wrote for standard WireGuard ( on my WRT32x ) ( on myGL-AR750S ) - I got the same results as you did. I got the same outcome - that being - It's still routing the traffic through my router to my ISP. But it's strange because on the main login page it shows I'm connected to a VPN. So, I wish you well.
Peace and God Bless