I found a prospective solution but the forum thread was dated way back in 22.
Noted here.
Either the pulls been merged into the code base or something, either way the artefacts are gone.
sudo rpi-update pulls/5744
*** Raspberry Pi firmware updater by Hexxeh, enhanced by AndrewS and Dom
*** Performing self-update
*** Relaunching after update
*** Raspberry Pi firmware updater by Hexxeh, enhanced by AndrewS and Dom
FW_REV:
BOOTLOADER_REV:2bfd7cb74e6bc16559e040d0f5d788a4411819e4
*** We're running for the first time
*** Backing up files (this will take a few minutes)
*** Remove old firmware backup
*** Backing up firmware
*** Remove old modules backup
*** Backing up modules 6.6.28+rpt-rpi-2712
WANT_32BIT:0 WANT_64BIT:1 WANT_PI4:1 WANT_PI5:1
Downloading bootloader tools
Downloading bootloader images
*** Downloading specific artifact revision (this will take a few minutes)
curl -L https://builds.raspberrypi.com/github/linux/11357ac4f0bb0dad2ac567a680ae469cd4dc6a86/bcmrpi | zcat | tar xf - -C //root/.rpi-firmware --strip-components=2
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
0 0 0 0 0 0 0 0 --:--:-- 0:00:04 --:--:-- 0
gzip: stdin: unexpected end of file
tar: This does not look like a tar archive
tar: Exiting with failure status due to previous errors
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
0 0 0 0 0 0 0 0 --:--:-- 0:00:04 --:--:-- 0
Invalid artifact specified. Response: 404.