iPad connected to LG Ultrafine 4K Display The Apple support document for the LG Ultrafine 4K display states here that only newer Macs are supported.
https://support.apple.com/HT207447

I was wondering if it is possible to use a Lighting to USB 3.1 Type C cable to transfer video+audio to the LG display. This following entry for a specific cable on Amazon mentions:

also supports USB quick charging, and high performance video and audio transfer


https://www.amazon.com/USB-3-1-Type-JOTO-White/dp/B01540Q4FK

Has someone tested this and can someone confirm that this is (not) working?
No, it will only charge the iPad.

Lightning doesn't have anything to do with HDMI. It's just a serial bus that cannot send any HDMI data without some help.

With Apple's Lightning Digital AV Adapter (which, in fact, is just small computer itself) you can output to an HDMI display. The native resolution is only 1600x900, however.