Enforcing IDE standardization for the team?

Do you guys work on a team where the IDE is standardized? Or is everyone free to use whatever IDE they want?

If developers are free to use whatever IDE they want, what are some best practices to ensure your codebase is truly IDE agnostic? Concrete example: code is Java based, and developers are using a mix of Eclipse, IntelliJ, and VS Code; using Maven for dependency management. What are some tips/tricks to minimize painful project imports?