Apple Watch Series 4 on iPhone SE (1st gen)

Hello.

I recently bought Apple Watch series 8 (paired with my iPhone 12 mini) and I discontinued the series 4.

I am trying to pair series 4 (with latest version of watchOS 9) to my old iPhone SE (with latest version of iOS 15) but I am not able to do it. It’s like watchOS is too much “updated” for iOS 15.

Is there a way to roll-back Apple Watch Series 4 to watchOS 8 (for example), even paying for the operation?

Thank you in advance for your help

Alessandro