I don't know what you mean by diagnostics tools; though @z7vl7abxc's suggestion of the bug-reporting (apport) tools make sense to me.
When you download Lubuntu (or any other Ubuntu ISO), there is a manifest file you can also download, which tells you what is included on the ISO and what you'll have available on install (though do note - some installers let you select specific types of installs (such as minimal) meaning whilst everything is installed; some packages can be removed at the end of the install to achieve your 'minimal' install option.. also the installer which exists on the ISO will get removed (won't exist on your installed system)).
These manifest files exist for all Ubuntu products (Server, Desktop), all Ubuntu flavors (like Lubuntu I'm using only as example) etc. They allow you to see a list of what packages are included, include package version details too, with the snap packages (if any are included) found at the bottom too. Knowing the package type allows easier removal (with the list mostly deb files, but all alternatives are easy to recognize, eg. snap packages start with 'snap:')
Generally if they are embedded into the OS you do not want to remove them, they may remove other things that might be dependent on them or some of their subfiles, if you do not use them just leave them where they are they won't hurt anything