Can also report that downgrading all the linux-firmware packages to 20251111 also worked for me without downgrading the kernel itself.
On Fedora Silverblue:
To downgrade to 20251111
rpm-ostree override replace \
https://kojipkgs.fedoraproject.org//packages/linux-firmware/20251111/1.fc43/noarch/linux-firmware-whence-20251111-1.fc43.noarch.rpm \
https://kojipkgs.fedoraproject.org//packages/linux-firmware/20251111/1.fc43/noarch/iwlwifi-mld-firmware-20251111-1.fc43.noarch.rpm \
https://kojipkgs.fedoraproject.org//packages/linux-firmware/20251111/1.fc43/noarch/linux-firmware-20251111-1.fc43.noarch.rpm \
https://kojipkgs.fedoraproject.org//packages/linux-firmware/20251111/1.fc43/noarch/iwlwifi-mvm-firmware-20251111-1.fc43.noarch.rpm \
https://kojipkgs.fedoraproject.org//packages/linux-firmware/20251111/1.fc43/noarch/amd-gpu-firmware-20251111-1.fc43.noarch.rpm \
https://kojipkgs.fedoraproject.org//packages/linux-firmware/20251111/1.fc43/noarch/amd-ucode-firmware-20251111-1.fc43.noarch.rpm \
https://kojipkgs.fedoraproject.org//packages/linux-firmware/20251111/1.fc43/noarch/atheros-firmware-20251111-1.fc43.noarch.rpm \
https://kojipkgs.fedoraproject.org//packages/linux-firmware/20251111/1.fc43/noarch/brcmfmac-firmware-20251111-1.fc43.noarch.rpm \
https://kojipkgs.fedoraproject.org//packages/linux-firmware/20251111/1.fc43/noarch/cirrus-audio-firmware-20251111-1.fc43.noarch.rpm \
https://kojipkgs.fedoraproject.org//packages/linux-firmware/20251111/1.fc43/noarch/intel-audio-firmware-20251111-1.fc43.noarch.rpm \
https://kojipkgs.fedoraproject.org//packages/linux-firmware/20251111/1.fc43/noarch/intel-gpu-firmware-20251111-1.fc43.noarch.rpm \
https://kojipkgs.fedoraproject.org//packages/linux-firmware/20251111/1.fc43/noarch/intel-vsc-firmware-20251111-1.fc43.noarch.rpm \
https://kojipkgs.fedoraproject.org//packages/linux-firmware/20251111/1.fc43/noarch/iwlegacy-firmware-20251111-1.fc43.noarch.rpm \
https://kojipkgs.fedoraproject.org//packages/linux-firmware/20251111/1.fc43/noarch/iwlwifi-dvm-firmware-20251111-1.fc43.noarch.rpm \
https://kojipkgs.fedoraproject.org//packages/linux-firmware/20251111/1.fc43/noarch/libertas-firmware-20251111-1.fc43.noarch.rpm \
https://kojipkgs.fedoraproject.org//packages/linux-firmware/20251111/1.fc43/noarch/mt7xxx-firmware-20251111-1.fc43.noarch.rpm \
https://kojipkgs.fedoraproject.org//packages/linux-firmware/20251111/1.fc43/noarch/nvidia-gpu-firmware-20251111-1.fc43.noarch.rpm \
https://kojipkgs.fedoraproject.org//packages/linux-firmware/20251111/1.fc43/noarch/nxpwireless-firmware-20251111-1.fc43.noarch.rpm \
https://kojipkgs.fedoraproject.org//packages/linux-firmware/20251111/1.fc43/noarch/qcom-wwan-firmware-20251111-1.fc43.noarch.rpm \
https://kojipkgs.fedoraproject.org//packages/linux-firmware/20251111/1.fc43/noarch/realtek-firmware-20251111-1.fc43.noarch.rpm \
https://kojipkgs.fedoraproject.org//packages/linux-firmware/20251111/1.fc43/noarch/tiwilink-firmware-20251111-1.fc43.noarch.rpm
rpm-ostree initramfs --enable
To undo the downgrade
rpm-ostree initramfs --disable
rpm-ostree override reset \
linux-firmware-whence \
iwlwifi-mld-firmware \
linux-firmware \
iwlwifi-mvm-firmware \
amd-gpu-firmware \
amd-ucode-firmware \
atheros-firmware \
brcmfmac-firmware \
cirrus-audio-firmware \
intel-audio-firmware \
intel-gpu-firmware \
intel-vsc-firmware \
iwlegacy-firmware \
iwlwifi-dvm-firmware \
libertas-firmware \
mt7xxx-firmware \
nvidia-gpu-firmware \
nxpwireless-firmware \
qcom-wwan-firmware \
realtek-firmware \
tiwilink-firmware