The difference is that, as of the past few releases, Ubuntu doesn't ship a -dbg kernel package in the main repository like Debian does. Instead they've come up with a new system to ship 'debug symbol' variants of all packages, with a -dbgsym suffix. But they ship them in a separate repository that isn't enabled by default, I guess to avoid confusing end-users (ddebs.ubuntu.com). So you need to configure that repository, install its key, then pull linux-image-$(uname -r)-dbgsym. I guess you might also want to pull the debug-symbol versions of the main libraries as well.
The difference is that, as of the past few releases, Ubuntu doesn't ship a -dbg kernel package in the main repository like Debian does. Instead they've come up with a new system to ship 'debug symbol' variants of all packages, with a -dbgsym suffix. But they ship them in a separate repository that isn't enabled by default, I guess to avoid confusing end-users (ddebs.ubuntu.com). So you need to configure that repository, install its key, then pull linux-image-$(uname -r)-dbgsym. I guess you might also want to pull the debug-symbol versions of the main libraries as well.