Which light switch is suitable for Philips Hue?

Yes
I only need a flush-mounted module that does not trigger the relay when the button is pressed or that has no relay at all and can be directly paired with the lamp via Zigbee binding

Does anyone possibly know such a flush-mounted module?

Hi Frank, BundJ used to have what you are looking for. It's called Light Link, very expensive and hard to program (I have some). However, by now there are several flush-mounted modules from other manufacturers, best to search for "flush-mounted Zigbee controller or device," I had a few on my radar in minutes, for example from the brand Led T R A D I N G, I can't say how good they are.

The Philips Hue lamps require continuous power, so we definitely have to replace the light switch.

Why? Just leave the normal light switch permanently on and control on/off by voice.

Yes
I just need a flush-mounted module that does not trigger the relay when the button is pressed or has no relay at all and can be paired directly with the lamp via Zigbee Binding.

Does anyone possibly know such a flush-mounted module?

Hm… we have buttons with piezo elements. The necessary voltage is generated when pressed - never have to change batteries. However, I didn’t get them myself and only assisted during installation, so I don’t know the brand right now. Just the hefty price of €60 per button.
Still a great solution. From visitors to the cleaning lady - not everyone wants to talk to the house. Also, the voice input had problems for 48 hours recently - then we resorted to button pressing again.

Why? Simply leave the normal light switch permanently on and control on/off via voice

For cases where it should be turned OFF without voice control. Also, I find it not smart to talk to Siri (in our case) when I’m standing right next to the switch panel in the hallway with shoes on anyway. Something doesn’t automatically become the better solution through voice control in every situation.

For the cases where it should be turned OFF without voice control. Also, I find it unsmart to talk to Siri (in our case) when I’m already standing next to the switch panel in the hallway with shoes on. Something doesn’t automatically become a better solution through voice control in every situation.

I can only speak for us; it has been working wonderfully in the dining room for all children and adults for 5.5 years.