Is Apple Watch with watchOS 9 compatible with iOS 15 iPhone?

..want give a new / new-ish Apple Watch (series 6 / 7 / 8) to an elderly family member who is still using an old iPhone (6S plus).

To install watchOS 9 a newer device is needed if I understand correctly - since this demands iOS 16, which in turn demands an iPhone 8 or newer - I have the same issue myself, can't update my Apple Watch 4 through my iPhone 6 as it's still on iOS 15 obviously (and, as a sidenote, can't update the watch directly to watchOS 9 via WiFi either).

My question:

can a new or (new-ish) Apple Watch (where watchOS 9 is already installed on the device) be used with and old (pre-sries 8) iPhone?

Thanks in advance!

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