It's me again. I found the following review text in the ratings regarding the Teleboy app:

Kalidromo
3 months ago - bought this product

Good value for money
Quick and relatively easy to set up the device. High quality. Good value for money. Zattoo app is not available for this device, but the Teleboy app is at least an equivalent alternative. Screws for the foot mount can only be screwed in with relatively great force and you have to be careful not to mess up the screw heads...😅. Unfortunately, no operating instructions are included in the scope of delivery, which have to be searched for in a somewhat complicated way on the web: https://www.documents.philips.com/assets......
All in all, I can highly recommend the device.

Why don't you ask Kalidromo directly?

I do not use the Teleboy app. I didn't find anything about dark mode in the user manual.
Otherwise, it's a TV you can't go wrong with.

Unfortunately I can't help you, I can't use the TV because I still haven't received the missing remote control in three weeks!!!!!