The safest starting point is the official TCL Support Page , where you can search by model number.
Sites like HardReset.info often host repositories of stock firmware for various P6046 models. firmware tcl u60p6046 link
This is the easiest way to ensure you have the stable version intended for your region. TCL U60P6046 (60", 4K, HDR): Price, specs and best deals The safest starting point is the official TCL