Unfortunately, the VLC player is currently not available on Titan OS. However, you can use the TV's integrated player.
According to the Philips instructions, you can play content over 4 GB.
The TV supports all common formats such as Dolby Vision, HDR10+, MKV, MPEG-4, MPEG-1 and 2, H.265 etc.
Go to the settings. Then go to General settings and there you must set the source (hdmi 1, hdmi 2, etc.) from Optimised to Standard and the dark spot should disappear.