You can download here (https://github.com/rdmato33/lidar_opendata) a shapefile or gpkg which list free lidar datasets. You can open it in QGIS in order to get the links to download them.
For benchmarking, I recommend you to use Vaihingen or Dublin datasets. There is also a new dataset you can use in Surrey, Canada (https://udayton.edu/engineering/research/centers/vision_lab/research/was_data_analysis_and_processing/dale.php).