I'm switching from Linux Mint to Ubuntu, having created an installer of 21.10 on a USB stick. When booting into the "Try Ubuntu" mode, my wifi adapter didn't work out of the box. So I went to the Additional Drivers section of the Software & Updates application and enabled the proprietary driver (Broadcom 802.11 Linux STA wireless driver source from bcmwl-kernel-source) for a BCM4352 802.11ac adapter.
That works like a charm. After enabling the driver, I can connect to a wifi network, browse the internet, etc... This is exactly what I had to do in Linux Mint as well, which isn't surprising since that one is based on Ubuntu.
So after confirming that wifi worked, I installed Ubuntu. I picked the option with the additional software and also checked the checkbox to install third party drivers. After the installation completes and I reboot into the new installation, I try to repeat the steps of enabling the wifi adapter, but when I click on Apply Changes, I get the error:
pk-client-error-quark: Cannot download packages whilst offline (257)
To try and fix the issue, I've plugged in the installation USB, went to the Ubuntu Software tab and made sure that it is checked in the "Installable from CD-ROM/DVD" section. No good. So I tested installing a random package from the command line with apt-get and the error message suggested that it was looking in /media/cdrom for the installation disk, where it was mounted in /media/username/[something]. So I created a link from the mount point to /media/cdrom and the command line installation worked.
But, activating the proprietary driver still returns the same error and it won't let me activate it.
It's a bit baffling that the process works perfectly fine in the "Try Ubuntu" mode, but it completely refuses to do the same thing when installed to disk.
