My question is, do you need to be logged into iCloud to use the RCS-enhanced on iOS 18 on a iPhone 15. I can not find a definitive answer to this even on Apple documentation.

The problem with the EU is that a lot of the counties are socialist leaning which is the exact opposite of the US and the everything that it represents when doing business. Microsoft went through this years ago with the early EU and now companies like Google, Apple and other are finding that they are hitting the proverbial brick wall with the EU. Apple will loose more in the long run if they don't abide with the socialist EU rules. 

It comes 45 years late. I might have done math when in school better than I did.

This brings up another disturbing scenario with Apple. If the photo's that you deleted years ago reappear what else is Apple storing on their servers that you have deleted from Data Recovery in iCloud. ARE THEY REALLY DELETED or are they just hidden like files hidden on a mac with a ".".. THe question now is can Apple be believed when they say they can not read your FileVault Key that might be stored on their servers and that in Systems Setting in Sonoma and is Advance System Protection, protection at all!

I have tried to avoid increasing my storage with Apple for that reason. Their hardware is pricey enough so I back most of my stuff up locally rather than have it stored on Apple servers since as we have seen not all are created equal. Dropbox comes to mind when I think about that, getting hacked twice in two years. I do have stuff on Apple and OneDrive but not stuff I would trust being accessed by Big Brother.