Thanks for your feedback @qubodup. Looks like the Subsurface AppImage is currently suffering from a known issue:
https://github.com/probonopd/AppImages/issues/83
Other AppImages might work though. So this is not a general limitation of the AppImage format but an issue with the example AppImage.
As a quick workaround, installing libselinux.so.1 from air should work. The proper solution, of course, is to compile the ingredients that go into the AppImage in a way that removes the libselinux.so.1 dependency, or to bundle libselinux.so.1 inside the AppImage. Another option might be to “preload a dummy libselinux that makes all child processes think that SELinux is disabled” as described in https://fedoraproject.org/wiki/Using_Mock_to_test_package_builds. Contributions in this area are highly welcome!