HMDI and composite video signals are vastly different. There are products out there that convert an HDMI signal to composite, but I don't know how well they work or what the price point is. Ben says it's not something he would bother attempting.
I don't understand exactly how the Nintendo Switch dock works, so does it convert the signal from the type-C usb to HDMI signal, or is it native HDMI signal and it just goes through the dock?
USB 3.1 type-C has an 'alternate mode' which now finally supports native HDMI 1.4b signalling, so the dock wouldn't necessarily need to convert the video signal if HDMI 1.4b Alt-Mode on USB Type-C was implemented on the Nintendo Switch.
(Other alternate modes supported are Display Port, MHL and Thunderbolt.)
Just a warning that the picture quality of composite video will be abysmal.
The display will look washed out and smudgy.
To improve picture quality that's why over the decades we moved from Composite Video (one analog signal), to S-Video (two analog signals), to Component Video (three analog signals) and now use pixelated digital video formats (often 3 digital channels over 6 wires).
The control we have with digital signalling (albeit with far greater and complex circuits) creates far superior images.
You won't know yourself if you upgrade to digital video and you'll probably have a far lower power bill to boot.
On a reddit post I saw, someone said that they were able to pull video from the Nintendo Switch's aux port. It was very bad video, but still video. Since my house is basically devoid of all HDTVs, I've been left to using composite video for almost everything. For instance my latest home console is the Wii U and that is probably the most current gen console that supports composite video (the reason being that it's just an overclocked Wii and the hardware was not very difficult to add.) Since I don't know squat about how electronics works I will throw like 2 ideas at the wall and see what sticks.
Idea #1: AUX port video execution
As seen here the quality is not very good but maybe there is potential. I don't know how it works or if it is even possible to replicate, but I figured it's worth an ask.
Idea #2: Nintendo Switch Dock Mod:
I don't understand exactly how the Nintendo Switch dock works, so does it convert the signal from the type-C usb to HDMI signal, or is it native HDMI signal and it just goes through the dock? Could this all be solved with a simple wire mod or will like a whole new conversion cable be necessary? Clarification and an explanation would be highly appreciated.
I'm new to this stuff so I'm really glad this community exists so I may learn