I want to suggest a new step

Which tool is this about? Where is its repository?

lensfun-update-data from https://github.com/lensfun/lensfun
Tool for upgrading database of correction files for lenses. It can be used to update system wide database or user base
https://github.com/lensfun/lensfun

Which operating systems are supported by this tool?

• linux
• mac-os
• windows via darktable/kipi ?

What should Topgrade do to figure out if the tool needs to be invoked?

check if lensfun-update-data command is available

Which exact commands should Topgrade run?

lensfun-update-data with root or without root permission depending if user prefer to update database system wide or not.