Haven't been able to enable the network adapter on my iMac19,1. I've had my phone tethered to my PC so I could work through different methods from this form and the Ubuntu forums without much success. Seems the issue has to do with an error with bcmwl-kernel-source? But I'm not entirely sure
Did you take a look at Software&Updates > Additional drivers if there is offered a WLAN driver?
Have you tried it with disabled secure boot in BIOS?
Would you please post the terminal output of
sudo lshw -C network
?
There are no drivers available.
I have been unsuccessful in trying to access BIOS, but booting into the Mac OS shows that it's functional
*-network UNCLAIMED
description: Network controller
product: BCM4364 802.11ac Wireless Network Adapter
vendor: Broadcom Inc. and subsidiaries
physical id: 0
bus info: pci@0000:03:00.0
version: 03
width: 64 bits
clock: 33MHz
capabilities: pm msi pciexpress cap_list
configuration: latency=0
resources: memory:81400000-81407fff memory:81000000-813fffff
*-network
description: Ethernet interface
product: NetXtreme BCM57766 Gigabit Ethernet PCIe
vendor: Broadcom Inc. and subsidiaries
physical id: 0
bus info: pci@0000:04:00.0
logical name: enp4s0f0
version: 01
serial: 38:f9:d3:0d:fa:91
capacity: 1Gbit/s
width: 64 bits
clock: 33MHz
capabilities: pm vpd msi msix pciexpress bus_master cap_list ethernet physical tp 10bt 10bt-fd 100bt 100bt-fd 1000bt 1000bt-fd autonegotiation
configuration: autonegotiation=on broadcast=yes driver=tg3 driverversion=6.14.0-37-generic firmware=57766a-v1.15 latency=0 link=no multicast=yes port=twisted pair
resources: irq:17 memory:b0200000-b020ffff memory:b0210000-b021ffff
*-network
description: Ethernet interface
physical id: 9
bus info: usb@1:5
logical name: enx2ac1a0560018
serial: 2a:c1:a0:56:00:18
capabilities: ethernet physical
configuration: broadcast=yes driver=ipheth driverversion=6.14.0-37-generic ip=172.20.10.2 link=yes multicast=yes
What I have found out so far is that it could be due to missing firmware.
All solutions I have seen first obtain the Apple firmware for the driver.
Here are a few helpful pages:
Be careful with this one, I haven't checked the script:
Try it with sudo apt install firmware-b43-installer bcmwl-kernel-source
If this shouldn't help, maybe this can:
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I'm a bit confused by "go to /usr/bin/firmware/brcm in the extracted folder and then copy the files to /usr/lib/firmware/brcm on the install", I don't see those paths in the folder nor can I find the second one
I suggest trying @Ponce-De-Leon's suggestion as the first easy step.
Broadcom locks all its drivers behind a proprietary license.
So GnuLinux distros are legally blocked from including them in the default build.
The End User, however, is not blocked - you can install them using the method Ponce suggested.
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Installed, but nothing happened 
When I couldn't figure out the first method, I attempted the other solution in that post, got this
tar (child): apple-bcm-firmware-14.0-1-any.pkg.tar.zst: Cannot open: No such file or directory
tar (child): Error is not recoverable: exiting now
tar: Child returned status 2
tar: Error is not recoverable: exiting now
Did you run this from the directory you downloaded the .tar into?
cd ~/Downloads
tar --use-compress-program=unzstd -xvf apple-bcm-firmware-14.0-1-any.pkg.tar.zst
Installing only means you installed the drivers... You may need to reboot or apply the drivers.
Run
lspci -nn | grep -i broadcom
And relay the results here.
That said - what you are doing at this moment is trying multiple methods all at once.
This can actually create Driver conflicts. The purpose of running lspci -nn | grep -i broadcom is to determine what driver you actually need - and apply that one.
Yes, after running that command with the folder in my desktop I rebooted my PC. Doing it from Downloads yield the same results
3:00.0 Network controller [0280]: Broadcom Inc. and subsidiaries BCM4364 802.11ac Wireless Network Adapter [14e4:4464] (rev 03)
04:00.0 Ethernet controller [0200]: Broadcom Inc. and subsidiaries NetXtreme BCM57766 Gigabit Ethernet PCIe [14e4:1686] (rev 01)
04:00.1 SD Host controller [0805]: Broadcom Inc. and subsidiaries BCM57765/57785 SDXC/MMC Card Reader [14e4:16bc] (rev 01)
BCM4364 is not supported by the open-source brcmsmac or b43 drivers.
So from @Ponce-De-Leon's earlier post, the firmware-b43-installer won't help.
But, the bcmwl-kernel-source should.
If you already ran Ponce's terminal command,
now try:
sudo modprobe -r b43 brcmsmac bcma
sudo modprobe wl
Running the Module Prober above should load the driver and result in immediate connection not requiring a reboot.
If that works, remember that if Secure Boot is enabled in BIOS, it will not allow the driver to boot, you will need to modprobe it again...
So you must disable Secure Boot to avoid that.
Was prompted to enter my password, but nothing seemed to happen?
The terminal will not relay much. Have you tested if you have net connection?
If you prefer to check with terminal:
ip link show
No discernible changes from what I can tell unfortunately
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: enp4s0f0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc mq state DOWN mode DEFAULT group default qlen 1000
link/ether 38:f9:d3:0d:fa:91 brd ff:ff:ff:ff:ff:ff
3: enx2ac1a0560018: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000
link/ether 2a:c1:a0:56:00:18 brd ff:ff:ff:ff:ff:ff
Ok, let's try:
sudo apt install --reinstall linux-headers-$(uname -r)
sudo apt install --reinstall bcmwl-kernel-source
sudo modprobe -r wl
sudo modprobe wl
I wonder if the kernel you are on is too new... That is a quite old networking card...
Before proceeding, when it says Setting up bcmwl-kernel-source (6.30.223.271+bdcom-23ubuntu1.1) ... should I wait? Or move forward with the other commands? I wasn't entirely sure the first time if I should have waited a certain amount of time before rebooting
Yes and you would have no choice, the terminal prompt won't appear until it finishes.
Also about rebooting - have you checked Secure boot?
Ok, noted 
I have attempted to but without much luck. Not sure if it's because I don't use a Mac keyboard but I could have sworn it was possible, as I've toyed around with demoing Mint and Ubuntu some time ago on this same PC
Oh right - mac. I do not believe that will have any secure boot option.
Ah I see.
When should I expect the process to complete?