When launched from the command line, it fails to load:

./Slacky-0.0.5-arm64.AppImage: error while loading shared libraries: libz.so: cannot open shared object file: No such file or directory

In the OS, package zlib has the following files installed:

• /usr/lib/aarch64-linux-gnu/libz.so.1
• /usr/lib/aarch64-linux-gnu/libz.so.1.3
  the first being a symlink to the second

The issue is fixed by created libz.so as a symlink to libz.so.1