I am working in Flame version 2026.2.2 and having a problem with the Machbox shaders for the first time, they are not visible in the node bin or in the search.
All of them are loaded via the default Matchbox node and are also functioning.
Have you installed any matchboxes recently? Similar thing happened to me and once I removed the most recently installed one and restarted the application, everything was back to normal.