Looking into the equivalent firmware[1] for my Archer C7 v2, I didn't find any OpenWRT bits though. I was honestly a little bit disappointed.

I guess the difference between hardware revisions might be more fundamental than I assumed.

    DECIMAL       HEXADECIMAL     DESCRIPTION
    --------------------------------------------------------------------------------------------------------
    0             0x0             TP-Link firmware header, firmware version: 1.-15188.3, image version: "",
                                  product ID: 0x0, product version: -956301310, kernel load address: 0x0,
                                  kernel entry point: 0x80002000, kernel offset: 16384512, kernel length:
                                  512, rootfs offset: 855873, rootfs length: 1048576, bootloader offset:
                                  15204352, bootloader length: 0
    71520         0x11760         Certificate in DER format (x509 v3), header length: 4, sequence length: 64
    98560         0x18100         U-Boot version string, "U-Boot 1.1.4 (Mar  5 2018 - 13:57:29)"
    98736         0x181B0         CRC32 polynomial table, big endian
    131584        0x20200         TP-Link firmware header, firmware version: 0.0.3, image version: "",
                                  product ID: 0x0, product version: -956301310, kernel load address: 0x0,
                                  kernel entry point: 0x80002000, kernel offset: 16252928, kernel length:
                                  512, rootfs offset: 855873, rootfs length: 1048576, bootloader offset:
                                  15204352, bootloader length: 0
    132096        0x20400         LZMA compressed data, properties: 0x5D, dictionary size: 33554432 bytes,
                                  uncompressed size: 2451644 bytes
    1180160       0x120200        Squashfs filesystem, little endian, version 4.0, compression:lzma, size:
                                  9878520 bytes, 789 inodes, blocksize: 131072 bytes, created: 2018-03-05
                                  06:16:10