Fixed that as well thanks to the community here - here's the full fix for your LG model:
1. Make sure the TV is set up properly i.e. Hit the Cog Wheel on the TV remote, scroll down the All Settings > Scroll down to General > Scroll down to HDMI ULTRA HD Deep Colour and make sure it's set to ON for the HDMI slot you'll be using for your PS4 Pro.
2. Set up the PS4 Pro as per the included Quick Start guide, but instead of Powering On, start the PS4 Pro in Safe Mode by pressing and holding the On switch for several seconds (you'll hear an initial beep, then a second beep which starts the PS4 Pro in Safe Mode at which point you can take your finger off the On switch).
3. In the PS4 Pro Safe Mode menu, set HDMI to 1.4 - if you leave it as Automatic it'll just power up with sound but no screen.
4. Hopefully your PS4 Pro is now displaying so you can set it up to your heart's content with old themes, signing in to PSN, transferring data over etc - however, couple of more steps needed now.
5. PS4 Pro > Settings > System > Enable HDCP - make sure box is ticked
6. PS4 Pro > Settings > Sound and Screen > Video Output Settings - make sure Resolution, RGB Range, HDR and Deep Colour Output are all set to Automatic.
Now the really clever bit:
7. Turn off the PS4 Pro, start it in SAFE MODE again.
8. Set HDCP in the Safe Mode menu back to Automatic.
If it's all done correctly - PS4 Pro > Settings > Sound and Screen > Video Output Settings > Video Output Information should look like this next time you view it:
Then if you want to see something really beautiful install and update The Last of Us Remastered. When it boots your TV will notify you that HDR is on via a pop up in the top right, and The Last of Us game will detect the presence of HDR and give you some extra options to try out:
Enjoy! Thanks to all contributors to this thread for making my PS4 Pro work as intended :)
