No network/wifi for new lubuntu install

[porphyry52]

Turns out its only on the largest ubuntu iso , so I got that and installed ubuntu side by side with Lubuntu. But no help, its Software Installer gives the cryptic message "Kernel source or headers are required to compile these modules", whatever that may mean.
All the online discussions of installing linux on this model asus referred to using a wifi dongle or even installing a different card in place of the Realtek, none mention a software solution.
Mine arrive tomorrow. I have high hopes for the dongle.

[praseodym]

With that CD applied as source, run

sudo apt update
sudo apt install --reinstall linux-image-$(uname -r) linux-headers-$(uname -r) linux-generic

Now, try it again

[porphyry52]

Both the dongle and the card arrived this am, and all I had to do was plug it in. Instant recognition and connection.

But I will also do the update and reinstall you recommend, I can use the usb port its plugged into for other purposes. Thank you for your help, and I'll let you know how it goes.

Immediately a problem. I'm not understanding what you mean by "...with that CD applied as source" do the 2 apt commands. man apt was not illuminating as to source. I inserted the 2.7gb ubuntu usb-stick, assuming this to be the source, and cd-ed to it in Terminal, and tried 'sudo apt update'. But of course it tries to make an internet connection.

[porphyry52]

So I couldn't update the system without internet, and can't compile the driver because other source code it needs that I got on the ubuntu.iso is older and out of sync with the driver code. So I should have downloaded the unstable ubuntu.iso as it would be more recent than the driver.

But I didn't. I plugged in the dongle, got connected and ran 'sudo apt update', and then 2-clicked the driver icon to install it.

No complaints about headers etc this time. What it said was "Cannot install from unsigned repo"

The moral of this story is: If your new computer needs a driver that is not already part of Linux, then a hardware solution always trumps attempting a software solution. The dongle (TP-Link USB WiFi Adapter for PC(TL-WN725N)) cost less than $8 and worked instantly. Its driver has long been a part of Linux.