QGIS 3.18 will have support for Point Clouds. If you want to create your own point clouds you need to watch this video.
You can create point clouds in a lot of ways, but in this video I will run through the process using Open Source tools and likely available sensors for most people.
I am using Open Drone Map, with WebODM to process geotagged photos.
https://www.opendronemap.org/webodm/
You can use any camera, but a GoPro with built in GPS works great and if you want to work with a georeferenced point cloud it is recommended that you use a camera with built in GPS so photos get geotagged (a smartphone will work).
To clean up the point cloud and extract "slices" I use CloudCompare.
http://cloudcompare.org/
The resulting LAZ/LAS point clouds are then loaded into QGIS 3.17 (development version of 3.18).
The final 3.18 version of QGIS will likely work slightly different from the master version I use.