Lidar can definitely be affected and cause focusing problems, but there’s protectors out there that have a hole for the lidar.

Image quality is affected, but in my testing the effects were minimal. I could only tell in side by side while zooming. If you intend to print your pictures in a large format at some point, then maybe it would matter, but if you keep the pictures phone sized then you won’t notice at all.

Also the worry of preventing lens scratches is real. Apple uses a sapphire lens that scratches easier than others, at about the same level that the front glass does. jerryrigeverything on YouTube has shown this repeatedly over the years.

Imo, lens protectors are no different that uv filters for lenses. Some people use them, some don’t. Both for their own reasons. Just do what makes you happy and content with your phone.