I’ve had the same issue as you for my VR project, the editor was crashing on load with those errors and I had issues pinpointing it to the LidarPointCloud Plugin.
For some reason I had that plugin turned on and wasn’t using it and couldn’t understand how migrating to 5.1 was crashing it. Luckily I ran into this post and fixed the issue (in my case, I turned off the plugin, but turning InstancedStereo off could also fix it)