Hi,
it looks like that there are different versions of the Archer D7 in field
My Archer-D7 is sold as AT/CH Version and has a different partition table like your
e.g. there is no "DECT" partition in my D7
My partition table looks liks
[ 0.916028] Creating 8 MTD partitions on "spi0.0":
[ 0.920892] 0x000000000000-0x000000020000 : "u-boot"
[ 0.927481] 0x000000020000-0x000000176400 : "kernel"
[ 0.934145] 0x000000176400-0x000000fc0000 : "rootfs"
[ 0.940402] mtd: device 2 (rootfs) set to be root filesystem
[ 0.946246] 1 squashfs-split partitions found on MTD device rootfs
[ 0.952531] 0x000000360000-0x000000fc0000 : "rootfs_data"
[ 0.959698] 0x000000fc0000-0x000000fd0000 : "config"
[ 0.966381] 0x000000fd0000-0x000000fe0000 : "romfs"
[ 0.972983] 0x000000fe0000-0x000000ff0000 : "rom"
[ 0.979345] 0x000000ff0000-0x000001000000 : "art"
[ 0.985760] 0x000000020000-0x000000fc0000 : "firmware"
in Openwrt specific is rootfs_data and firmware, original firmware is without that both