I have installed Ubuntu 18.04 on my mid-2009 MacBook Pro, however, I am unable to even search for a wireless internet connection.
I have searched past question from this site and askubuntu re; no wi-fi adapter found, and found they either refer to past versions of Ubuntu or their implementation strategies (e.g.
sudo update) does not to MacBooks or don’t work because they rely on internet connection that I do not have (e.g. sudo…reinstall kernel source).
I think I have the exact same hardware (13 inches?) and OS installed, and I too had problems with my wifi card. The easiest workaround is to have an Ethernet connection while you install Ubuntu and check the "install proprietary drivers", but I guess it's too late for that one.
Still, you will need an internet connection through Ethernet to solve this, as you have to download and install the drivers.
If you open "Software & Updates" and go to the "Additional Drivers" tab, what do you see? It should look similar to my screenshot.
Make sure "Using Broadcom 802.11 ..." is selected, probably it says "Do not use this device". Once you click the other radio button and then hit apply, it should download and install the driver.