Both Intellij and Eclipse are supported out of the box.
For Solr 9x and later, executing "gradlew tasks" will list a section "IDE tasks" to get you started. The dev mailing list or the slack solr-dev channel are good places for detailed questions.
Run the following to set up Eclipse project files:
./gradlew eclipse
then import the project into Eclipse with:
File → Import… → Existing Project into Workspace
Please note that Eclipse does not distinguish between sub-projects and package sets (main/ test) so pretty much all the sources and dependencies are available in one large bin.