QuPath extension catalog from the TIA Centre, University of Warwick. Currently lists the TIAToolbox QuPath extension, which runs TIAToolbox models from inside QuPath.
In QuPath, open "Extensions" → "Manage extensions" → "Manage extension catalogs" → copy & paste below text to the bar → click "Add":
https://github.com/TissueImageAnalytics/qupath-catalog
The extension will appear in the list. Install it and restart QuPath.