Can lidar be purchased for hobbyist use yet?
Depends on your budget and the resolution you need.
E.g Livox mid 360 https://store.dji.com/en/product/livox-mid-360
I haven’t done it myself but I’ve heard of people harvesting LiDAR units from their old/broken robot vacuums.
Check out PiLIDAR for one of many options:
Sure. Line scan indoor units are extremely affordable, and some cost less that $20, sold as spare parts for robot vacuum cleaners. Outdoor units (with higher ambient light tolerance and longer range) are an order of magnitude more expensive, but also available.
Here is some detailed information about low cost units: https://github.com/kaiaai/awesome-2d-lidars/blob/main/README...