UPDATE: Folks may have better results and control with CloudCompare, see my tutorial on that workflow at    • QGIS 4 Arch – LiDAR to DEM & DSM with...  

QGIS4Arch is a free online course for learning QGIS, an open source geographic information system (GIS) software package. This course is for those who works with cultural heritage resources, including archaeologists, architectural historians, and historians. The course is designed to take you from beginner to expert. This video uses QGIS Latest Release version 3.12.

This lesson examines the use of LASTools within QGIS to convert a LiDAR point cloud to a digital elevation model (DEM).

LASTools https://rapidlasso.com/lastools/downl...
The National Map https://viewer.nationalmap.gov/basic/

Timestamps:
0:10 Topics for this lesson.
0:59 Installing LASTools.
2:15 Downloading LiDAR data.
3:35 Inspecting LiDAR data using LASInfo.
5:06 Dividing/Splitting LiDAR data.
6:54 Converting divided data to DEM files.
8:26 Merge and symbolize DEM.

Download the LiDAR (.laz) file here (copy and paste into browser URL field) ftp://rockyftp.cr.usgs.gov/vdelivery/Datasets/Staged/Elevation/LPC/Projects/USGS_LPC_AR_R6_WashingtonCO_2015_LAS_2016/laz/USGS_LPC_AR_R6_WashingtonCO_2015_15suv930915_LAS_2016.laz