We are using Sharepoint 2013 on-prem. We have couple of projects/wsps developed in sandbox solutions. Now we require this project in shrepoint 2019 on-premise with content db upgrade solution. Does Sharepoint 2019 on-premise supports sandbox solutions or entire sandbox solutions need to be rewritten with spfx/hosted app etc...? I know for Sharepoint online we have to rewrite but not sure for Sharepoint 2019 on premise. Can you please suggest what can be done?