To understand the firmware, you must first understand the silicon. The 43W800C uses a (sometimes referenced as a dual-core ARM Cortex-A17). This was Sony’s first major foray into offloading smart features from their proprietary X-Reality Pro chip to a third-party SoC.
If your TV's built-in update fails or says it's up to date but you're on an older version (e.g., version 7 or lower), you may need a manual file: firmware sony 43w800c