If I’m reading this correctly, my understanding is that “multi-level” source maps merely refers to generating a single source map using multiple build steps, i.e. CoffeeScript => Uglify => final minified JS (2 steps). It still produces a single source map file that should map your final code to your original source code.
In which case, Sentry should support this. Ultimately we use the source map to just match your production files/lines/columns back to their original locations. How they are built doesn’t really matter, as long as they correctly have this mapping.
At the very end of Rollbar’s docs on source map usage, the last bullet point on debugging, they reference not supporting this: https://rollbar.com/docs/source-maps/2
Are you referring to this?
Some source map generation tools support an alternate representation of the map that combines multiple sub-maps into “sections” within the top level map. Each section can either be embedded source map or a reference to an external source map. Unfortunately, we don’t yet support this source map format.
These are called “indexed” source maps, and Sentry does support them (!). I don’t think this is what you’re referring to, though. But they are generated by some build tools, i.e. the React Native bundler, and are interpreted correctly by Sentry.