virtualbox.org

This didn't work:
Nor:
So I clicked on Devices > Insert Guest Additions CD image. A pop-up Given the option to open in the file manager, so I clicked okay. I pressed F4 to open in terminal and ran:
And got:

The error in the screenshot is because the header command didn't work.

Please see https://www.virtualbox.org/manual/ch02. ... nux-prereq for the prerequisites for official Guest Additions in the VM, same as for Virtualbox on the host (also https://www.virtualbox.org/manual/ch04. ... ions-linux). You'll note there's no mention of dkms, so the instructions you used for the commands above are non-official sources that we cannot help with.

I also did not have success inserting the '(uname -r)' into the apt install command. Per the linked instructions, run the "uname -r" as a separate command, then paste the result into the apt command.

If you have trouble, please elaborate more on what the trouble is:

LPIII wrote:This didn't work:

isn't distinctive enough to help with.

@LPIII

The output from the attempted Guest Additions install states that the "gcc make perl" packages are missing from your Lubuntu VM and explicitly asks for them to be installed, so you need to try:
If the installation of the other dependencies required hadn't completed when you issued the commands then you should have seen an error message.

It turns out that I just needed to run:
Before:
And to installe the guest additions I needed to go to:
Open in the terminal and:

Great! Glad you're up and running.