If you are using Public Folders (legacy or Modern) and would like to migrate some of them to Office 365 Groups, the Exchange team is working on a solution for that. They are starting with the migration of Calendar folders and will move on to other types as we complete work on calendars. The team would like to have customers who want to try this migration to provide feedback. You can also send your information if you would like to try migrating other types of public folders (other than Calendar) as the team extends the support to those folder types.
If you're interested in trying this migration, read this blog for more information.