The other Linux binaries are still being built and will be available over the course of the next couple of hours. The Windows and macOS binaries as well as the Linux AppImage are available already. You can download the source code or one of the binaries. Fortunately they were only annoying but didn’t affect existing files.
MKVToolNix v78 is out with tons of bug fixes, especially for those crashes in the GUI’s header editor & for the GUI hanging when adding files via drag & drop.