Using ChrisG's method I was able to connect as well (thanks Chris).
My router broadcasts on 5Ghz and 2.4Ghz. With some experimenting I found that the LG TV can connected to the router on 2.4 or 5 or even Ethernet cable, but the PC only works when it is connected to wifi on the 2.4Ghz band. When the computer is connected, on the LG TV go to Settings > Advanced > Network > Wi-Fi Connection and you should see your computer listed with DIRECT-Yourcomputername. So it appears that the PC connects directly to the TV, but only on the 2.4Ghz band.
So the complete solution is:
Connect your PC to your wireless network using the 2.4Ghz band.
Start Screen Share on the LG TV. Under Connection Options, I found normal mode worked better than fast mode.
In Windows 10, press Windows + P to open the projection display settings, then select Connect to a wireless display.
Hopefully it connects. Good luck!
I hope this helps, disappointing that LG support wasn't able to figure this out for people.