Does 4K remote work with ir repeater

The Siri Remote work with Bluetooth, for everything but volume control. Volume control is done via IR directly with the TV or wired audio equipment, not through the Apple TV box.

The Apple TV 4K box can work with an IR repeater/extender, when used with IR remotes.

Use other remotes to control Apple TV - Apple Support

Hello echodm,

We understand that you would like to use your Siri Remote with an IR repeater. We’d like to help however we can. 

You can learn how to use your Siri Remote using an IR sensor here:

Control your TV or receiver with your Siri Remote or Apple TV Remote

If you are trying to do something else with your Siri Remote, please provide more details. 

Thanks!