V10.4.0, being the end of a major cycle, is rock-solid. It rarely crashes, and its brushing engine is predictable.
For more details on how to use these tools, you can explore the Lightroom Classic User Guide troubleshooting a particular issue in this version? What's New in Lightroom Classic and Cloud-Based Lightroom 17 Aug 2021 — Adobe Photoshop Lightroom Classic 2021 v10.4.0