I am installing on an Asus PN51-E1 which includes the Mediatek MT7921e wifi device.
I came across this bug while trying to install from https://cdimage.debian.org/cdimage/bookworm_di_alpha2/ netinst iso on a USB stick. I see the same error, but what I was trying to debug when I arrived at this bug is why we see the error in dmesg: mt7921e 0000:05:00.0: firmware: failed to load mediatek/WIFI_MT7961_patch_mcu_1_2_hdr.bin (-2) because when I break to the console in the installer, I see in /lib/firmware this very file: ~ # ls /lib/firmware/mediatek/WIFI_* WIFI_MT7922_patch_mcu_1_1_hdr.bin WIFI_MT7961_patch_mcu_1_2_hdr.bin WIFI_RAM_CODE_MT7922_1.bin WIFI_RAM_CODE_MT7961_1.bin When I tried again in Expert install mode, I looked before detecting network devices, and saw that /lib/firmware was empty. What's populating this directory? Is it a chroot and thus the kernel module can't see it? Or... is the kernel module looking in a different path?
