Gaming keyboards from high-quality brands also on the Ps4?

I've been looking for a gaming keyboard for the Ps4 for a long time but only ever find some 10 Euro scrap. That's why I would like to know whether you can also find keyboards from e.g. Asus, Roccat or Razer.

Sure, of course. Everything that has a USB port can be connected. Just go to the online shop of Razer and Co. And see if you can find something suitable for you.

The Apex range is compatible with the Ps4 and I already had the 7 was quite satisfied

You can connect any PC keyboard to the Playstation whether the game supports the whole thing is another question