The issue would seem to be resolved after running for more than a week without failing.

So the firmware I have used looks to be good on a RPi3B

Nice to hear that
In my opinion, your missing NVRAM file could very well had being the culprit

So the firmware I have used looks to be good on a RPi3B

The issue is firmware, rather than an actual arm specific driver, which is under the non-free packages.

Duck diving found plenty of reports of issues for the firmware including the "Firmware has halted or crashed" over several years, and I concluded that picking a stable one was going to be hit or miss.

re: [    6.113164] brcmfmac mmc1:0001:1: Direct firmware load for brcm/brcmfmac43430-sdio.raspberrypi,3-model-b.txt failed with error -2]

I think this error means the file is not present, and the error has gone since I added one.

After trying several firmware versions with limited or no success, I am currently testing this one:

from firmware-brcm80211_20210818-1_all.deb
(http://ftp.br.debian.org/debian/pool/no … -1_all.deb)

these extracted files were added or replaced in /lib/firmware/brcm/

brcmfmac43455-sdio.raspberrypi,3-model-b.txt
brcmfmac43430-sdio.bin
brcmfmac43430-sdio.clm_blob

which contains this version:  Firmware: BCM43430/1 wl0: Mar 30 2021 01:12:21 version 7.45.98.118 (7d96287 CY) FWID 01-32059766

I'll now have to wait and see how long it runs. It typically stopped in less than a week.

Mark.

[    6.023803] brcmfmac: brcmf_fw_alloc_request: using brcm/brcmfmac43430-sdio for chip BCM43430/1
[    6.035938] usbcore: registered new interface driver brcmfmac
[    6.113164] brcmfmac mmc1:0001:1: Direct firmware load for brcm/brcmfmac43430-sdio.raspberrypi,3-model-b.txt failed with error -2
[    6.367776] brcmfmac: brcmf_fw_alloc_request: using brcm/brcmfmac43430-sdio for chip BCM43430/1
[    6.400889] brcmfmac: brcmf_c_preinit_dcmds: Firmware: BCM43430/1 wl0: Sep 11 2018 09:22:09 version 7.45.98.65 (r707797 CY) FWID 01-b54727f
[    6.785619] brcmfmac: brcmf_cfg80211_set_power_mgmt: power save enabled
[   44.549152] brcmfmac: brcmf_cfg80211_set_power_mgmt: power save disabled

hello, were to you got the NVRAM file 'brcmfmac43430-sdio.raspberrypi,3-model-b.txt' from?
try to find that file in the '/lib/firmware' folder, I don't know if its relevant for your error,but that file has configurations for the device..
does you changed it?

[    6.113164] brcmfmac mmc1:0001:1: Direct firmware load for brcm/brcmfmac43430-sdio.raspberrypi,3-model-b.txt failed with error -2

I suggest you look here for native drivers. Do ofcourse Debian with Devuan :-=

Have an ice day and may DuckDuckGo enlighten you
Lars H

EDIT: Forgot the link https://wiki.debian.org/brcmfmac

I am using beowulf on Pi 3B as the host for a  Home Automation platform.
It has been stable, apart from the wifi.

Wifi is configured as just an access point for the automation networking to Sonoff and other wifi devices, and with ethernet for the lan side.
It all runs fine for a few days, and then the wifi firmware crashes, disabling the wifi.

wifi power management has been disabled, but that didn't resolve the crashes.

boot up looks ok.

[    6.023803] brcmfmac: brcmf_fw_alloc_request: using brcm/brcmfmac43430-sdio for chip BCM43430/1
[    6.035938] usbcore: registered new interface driver brcmfmac
[    6.113164] brcmfmac mmc1:0001:1: Direct firmware load for brcm/brcmfmac43430-sdio.raspberrypi,3-model-b.txt failed with error -2
[    6.367776] brcmfmac: brcmf_fw_alloc_request: using brcm/brcmfmac43430-sdio for chip BCM43430/1
[    6.400889] brcmfmac: brcmf_c_preinit_dcmds: Firmware: BCM43430/1 wl0: Sep 11 2018 09:22:09 version 7.45.98.65 (r707797 CY) FWID 01-b54727f
[    6.785619] brcmfmac: brcmf_cfg80211_set_power_mgmt: power save enabled
[   44.549152] brcmfmac: brcmf_cfg80211_set_power_mgmt: power save disabled

then it dies

[782513.562083] ieee80211 phy0: brcmf_fw_crashed: Firmware has halted or crashed
[782710.159094] ieee80211 phy0: brcmf_proto_bcdc_query_dcmd: brcmf_proto_bcdc_msg failed w/status -110
[782712.719092] ieee80211 phy0: brcmf_proto_bcdc_query_dcmd: brcmf_proto_bcdc_msg failed w/status -110
[782712.719110] ieee80211 phy0: brcmf_cfg80211_get_station: GET STA INFO failed, -110
[782732.879131] ieee80211 phy0: brcmf_proto_bcdc_query_dcmd: brcmf_proto_bcdc_msg failed w/status -11

current firmware

firmware-brcm80211/stable 20190114-2 all
Binary firmware for Broadcom/Cypress 802.11 wireless cards

I tried adding a pi 3b specific nvram file and different firmware files, but was unable to get a working combination.

Has anyone else seen and fixed this issue or managed to update wifi firmware for the Pi 3 B?

There are multiple recent reports of the wifi firmware crash issue on this and other pi models.
Mark.