I would expect them to be there but debuginfod for Ubuntu is very new and did not (at least currently) import older releases (including the current LTS) or older package versions. Which is maybe what you’re seeing. Should work better with the most recent release only.

Do you have a specific example of which executables are missing?

There are also other ways to get all the debug symbols but it’s much fiddlier and not nearly as nice as debuginfod. Data’s all there, finding it is harder. You can query the apt index for buildids but only for the currently released package version and not superseded ones.

There were discussions about importing all the history and a way to do it was determined but not sure where the implementation of that has gotten too.