Unblocking a trapless (?) shower drain

My mother's shower is draining very slowly. She has tried putting domestos down it with no real effect.

I looked at videos on Youtube on how to solve this but all of the showers they show have a removable trap they they remove and clean. The shower I need to unblock doesn't seem to have anything you can remove. (I'll attach a picture.) (Possibly, as it is in a wet room it is not like other shower drains.)

What's the best way of unblocking a shower drain like this?

Cheers.

The central portion of that trap may pull right out. You may need to make a couple of L-shaped hooks to get under the lip in the well to facilitate pulling.
If it does then you'll get direct access to the drain line. When refitting ensure you apply suitable lubricant to the sealing ring.

Cheap £30 wet-vac?