Gitlab 18.0 has been released. Since there are breaking changes the update will be postponed to July 2025. For a list of breaking changes see https://about.gitlab.com/blog/2025/04/18/a-guide-to-the-breaking-changes-in-gitlab-18-0/. Please prepare yourself and your projects for this update.
This has proper support for rollup while providing the same API.
This is what open-wc recommends now and uses in their @open-wc/testing package