I am running SketchUp Pro 2019 on a MBP Late 2013 on MacOS 11.7.10
After reinstallation of SU most of my add-ons are gone.
In particular I am looking for a claenup3 add-on in a version that runs on SU Pro 2019. The ones I found ask for updating SU to the latest version, wich I don’t like to do.
Unfortunately old a lot of the plugins had to be fixed or recoded to make them work with the new sketchup’s api, the problem is also from the other side, some plugins that work on older versions of sketchup, don’t work on newer versions cause the developer doesn’t work on them anymore. You could try contacting @thomthom and ask him if he could give you a previous version of cleaneup or a script
Either update to a version of SketchUp that is supported by the Extension Warehouse (along with upgrading your computer) or go to the Extension Warehouse in your web browser and download the extension to your computer. Then you can install it via Extension Manager.