How to offline install of Spring Boot Tools Plugin into Eclipse IDE?
Here is the archived update site for STS 4.4.2 for Eclipse 2019-09:
It contains all the STS4 pieces and a bunch of additional plugins from Eclipse, we havent really tested a full offline installation using purely this update site. Usually the install procedure contains other update sites while installing a feature in order to find missing dependencies. So in case you dont have internet access and the STS4 install requires a dependency that usually comes from the main Eclipse p2 repo, you might run into this. In that case, please open a bug at https://github.com/spring-projects/sts4/issues and we will fix that.
Hope this helps!