Ubuntu 21.04 dual boot on iMac BigSur Wireless Device not supported

I have Ubuntu 21.04 and MacOS BigSur setup to dual boot. Using ioreg -l | grep RequestedFiles, I have obtained my MacOS driver information.

"RequestedFiles" = ({
"Firmware"="C-4364__s-B2/nihau.trx",
"TxCap"="C-4364__s-B2/nihau-X0.txcb",
"Regulatory"="C-4364__s-B2/nihau-X0.clmb","NVRAM"="C-4364__s-B2/P-nihau-X0_M-HRPN_V-m__m-7.7.txt"})'

I copied these files and renamed them accordingly in my Ubuntu install brcmfmac4364-pcie.bin, brcmfmac4364-pcie.clm_blob, brcmfmac4364-pcie.Apple Inc.-iMac,2.txt.

I run sudo modprobe -r brcmfmac && sudo modprobe brcmfmac to reload the modules but I can see the failure to load of -2. When I run journalctl -k --grep=brcmfmac

From all of the supported firmware lists I can find, I don't see BCM4363 listed or the ID 14e4:4464. I believe my hardware is new enough it isn't in the included drivers. Has anyone else figure out how to get their Wi-Fi working?

Ok, the command you gave me was really helpful. I did a little more work on my own. I found on this site (https://itectec.com/ubuntu/ubuntu-how-to-activate-wifi-on-bcm4364-using-brcmfac-driver-firmware/) that they used a different firmware. Most of my understanding of what to do came from here (https://wiki.t2linux.org/guides/wifi/). I just didn't use the firmware from my own machine. I also had to follow the instructions at the bottom to get WPS2 to work.

Here is how I installed my firmware:

wget https://packages.aunali1.com/apple/wifi-fw/18G2022/C-4364__s-B2/kauai.trx sudo cp kauai.trx /lib/firmware/brcm/brcmfmac4364-pcie.bin

wget https://packages.aunali1.com/apple/wifi-fw/18G2022/C-4364__s-B2/nihau-X0.clmb sudo cp nihau-X0.clmb /lib/firmware/brcm/brcmfmac4364-pcie.clm_blob

wget https://packages.aunali1.com/apple/wifi-fw/18G2022/C-4364__s-B2/P-nihau-X0_M-HRPN_V-m__m-7.7.txt sudo cp P-nihau-X0_M-HRPN_V-m__m-7.7.txt /lib/firmware/brcm/brcmfmac4364-pcie.Apple\ Inc.-iMac19,2.txt

Then I rebooted.

Thanks so much for your help chili555. I was just stuck and needed a tip to get over the hump.