You shouldn't have to install third-party drivers, the linux kernel
usually supports mainstream hardware out of the box. There are
exceptions though - fancy printers/scanners, exotic hardware, closed
hardware difficult to reverse-engineer, and/or hardware that is too new
for support to have reached the stable kernels used in Qubes, ...
By the way installing vendor drivers is quite a painful and time
consuming process.
What is your wireless adapter based on ? USB ? PCIe ? If you have
another computer with a "standard" linux distribution installed - eg.
debian, fedora, ubuntu, ... - did you try your adapter there ?
If your adapter is a PCIe card, did you assign it to sys-net ? Do you
see anything relevant in `sudo dmesg` in sys-net ?
Otherwise, assuming it's a USB device, is it shown when typing `lsusb`
in sys-usb (assuming you have such vm) ? Ditto for `sudo dmesg` ?
Or maybe your adapter is supported but you simply didn't configure your
VM(s) to use it - eg.:
1- attach the device from sys-usb to sys-net (not guaranteed to work -
usb pass-through is usually a hit or miss)
2- or, attach the relevant usb controller(s) to sys-net (and ditch
sys-usb if it doesn't have controllers assigned to it anymore).
3- or, setting up NetworkManager in sys-usb and defining 'sys-usb' as
sys-firewall's netvm (which basically ends up being identical to 2- above).
(note: I don't have a usb network adapter to test so the above is what I
imagine is needed given my knowledge of qubes. Others may chime in...).
The following may also help:
https://www.qubes-os.org/doc/usb/
Ivan