$ ffmpeg -i 01\ -\ The\ Message.flac -c:v copy -c:a alac output.m4a
ffmpeg version 3.4.6-0ubuntu0.18.04.1 Copyright (c) 2000-2019 the FFmpeg developers
  built with gcc 7 (Ubuntu 7.3.0-16ubuntu3)
  configuration: --prefix=/usr --extra-version=0ubuntu0.18.04.1 --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --enable-gpl --disable-stripping --enable-avresample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librubberband --enable-librsvg --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-omx --enable-openal --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libopencv --enable-libx264 --enable-shared
  libavutil      55. 78.100 / 55. 78.100
  libavcodec     57.107.100 / 57.107.100
  libavformat    57. 83.100 / 57. 83.100
  libavdevice    57. 10.100 / 57. 10.100
  libavfilter     6.107.100 /  6.107.100
  libavresample   3.  7.  0 /  3.  7.  0
  libswscale      4.  8.100 /  4.  8.100
  libswresample   2.  9.100 /  2.  9.100
  libpostproc    54.  7.100 / 54.  7.100
Input #0, flac, from '01 - The Message.flac':
  Metadata:
    TITLE           : The Message
    ARTIST          : Prolix;Black Sun Empire
    ALBUM           : The Message
    album_artist    : Prolix;Black Sun Empire
    track           : 1
    disc            : 1
    GENRE           : Electro;Dance
    DATE            : 2018-07-27
    LENGTH          : 320
    BPM             : 173.71
    PUBLISHER       : Blackout Music NL
    ISRC            : USA2P1843097
    BARCODE         : 192641122873
    COMPILATION     : 1
  Duration: 00:05:20.03, start: 0.000000, bitrate: 1113 kb/s
    Stream #0:0: Audio: flac, 44100 Hz, stereo, s16
    Stream #0:1: Video: mjpeg, yuvj444p(pc, bt470bg/unknown/unknown), 800x800 [SAR 300:300 DAR 1:1], 90k tbr, 90k tbn, 90k tbc
    Metadata:
      comment         : Cover (front)
Stream mapping:
  Stream #0:1 -> #0:0 (copy)
  Stream #0:0 -> #0:1 (flac (native) -> alac (native))
Press [q] to stop, [?] for help
[ipod @ 0x560d11737740] Could not find tag for codec mjpeg in stream #0, codec not currently supported in container
Could not write header for output file #0 (incorrect codec parameters ?): Invalid argument
Error initializing output stream 0:1 --
Conversion failed!