First entry titled "Latest git master" contains binary with latest changes to the application.
Entries below are stable releases.
For instructions on how to start AppImage look here
Building from sources
Subtitle Composer can be built/installed on all linux distributions. Since recently windows support has been added to KDE Frameworks 5, so in theory it should be possible to build it there too, instructions will be added as soon as I manage to try it out.
Most linux distributions should already include Subtitle Composer. If you want to build latest version from git yourself instructions can be found here.
Submitting useful stack trace and good crash reports
Subtitle Composer installed from your distro repository is likely not reflecting latest version and very likely is missing the debug symbols. To paste useful stack trace in bug report please do following:
Build the application with debug symbols - instructions should take you around 20 minutes