Strange the package is not found if I type in mt76x2 in the Plug-Ins GL GUI.
I use GL-MV1000 release of GL-iNet GUI is 3.203.

I logged in via ssh and executed opkg list | grep *mt76* that showed me the packages.
I installed it with opkg install kmod-mt76x2

There is also a kmod-mt76 meta package available but I’m uncertain if this is required for the Wifi USB stick?!