This CLI command will move any known legacy XF1 file into a specially created _legacy directory. From there, you can either archive or remove that directory.
This will not necessarily move all add-on files. It will move any files stored under the old library directory, but other files these add-ons create may still remain. You would have to contact the author of any add-on to check if there are other files which are safe to move.
To run the command, type the following while in your XF root:
php cmd.php xf:legacy-cleanup
If you're on a server where you do not have access to the shell, please ask your server admin or host to run the command for you. If that is not possible, open the file
src/addons/XF1Cleanup/Cli/Command/LegacyCleanup.phpand look for the list of $files and the list of $dirs to learn which files/directories can be removed manually.
Please make a backup of your files before attempting to run this command.