Is Apple Watch SE 1 (2020) compatible with iPhone XR iOS 18.1.1?

Yeah it is. But there's a catch... When iPhone XR will not have in future the newest iOS than if you want to update your watch you cannot becose on iPhone must be iOS the same generation like your iPhone

Example :

iOS 17 = WatchOS 10

iOS 18 = WatchOS 11

iPhone XR is now the oldest compatible iphone with iOS 18

When will be iOS 19 it maybe be llike you cannot download it on XR

But Watch will be compatible with WatchOS 12

But if you have iOS 18 and wanna download WatchOS 12 you cannot

Hope will help but yeah sure it it compatible

Jzapko