Udon script that exposes additional options for mirrors giving the ability to set distance based culling per layer functioning like an adjustable far clip distance.
Add this script to any existing mirror or use the included mirror prefab.
Setting the culling distance to 0 will disable culling behaviour for that layer.
Settings used for the video example.
An example world that contains a mirror with this script applied can be found here:
https://vrchat.com/home/world/wrld_6eaf7a85-ffcb-4765-a9b6-c7e435802079