The Apple Watch SE A2351 is still supported but it only goes up to 10.6 according to gsmarena and Tom’s Guide

https://endoflife.date/apple-watch

https://www.gsmarena.com/apple_watch_se-10446.php

We have bad news for people with Apple Watch Series 4, Apple Watch Series 5, and the original Apple Watch SE (2020). Apple has just revealed that OS software updates will no longer be supported for either watch, taking effect with the release of watchOS 11.

https://www.tomsguide.com/wellness/smartwatches/watchos-11-compatibility-see-if-your-apple-watch-is-update-eligible