I just downloaded the Linux version of 1.3.0 and tried to run both the lovely_composer.AppImage and the config.AppImage and both had the same traceback when running them from console:

Traceback (most recent call last):
    File "/tmp/.mount_lovely3oSm6E/lovely_composer.py", line 4, in <module>
    File "<frozen importlib._bootstrap>", line 1007, in _find_and_load
    File "<frozen importlib._bootstrap>", line 986, in _find_and_load_unlocked
    File "<frozen importlib._bootstrap>", line 680, in _load_unlocked
    File "/tmp/.mount_lovely3oSm6E/doxel/__init__.py", line 10, in <module doxel>
    File "<frozen importlib._bootstrap>", line 1007, in _find_and_load
    File "<frozen importlib._bootstrap>", line 986, in _find_and_load_unlocked
    File "<frozen importlib._bootstrap>", line 680, in _load_unlocked
    File "/tmp/.mount_lovely3oSm6E/doxel/core/__init__.py", line 42, in <module doxel.core>
    File "/tmp/.mount_lovely3oSm6E/doxel/core/__init__.py", line 39, in _load_library
    File "/tmp/.mount_lovely3oSm6E/ctypes/__init__.py", line 452, in LoadLibrary
    File "/tmp/.mount_lovely3oSm6E/ctypes/__init__.py", line 374, in __init__ 
OSError: libtiff.so.5: cannot open shared object file: No such file or directory

I'm running the latest version of Manjaro Linux (an Arch based distro). I have libtiff (both 32 and 64bit versions) installed from my distro's repos. But usually with AppImages they've got everything they need to run included within their package. So my suspicion is that libtiff was mistakenly left out of the AppImage build. Not sure if any other libraries are missing, but it would be worth double checking on your end, as these sorts of missing library errors stop at the first instance of something missing, so any others are ignored until that first missing requirement is satisfied.