Yesterday, after a late-night update (Poland), I encountered the exact same problem. After an hour-long conversation with a senior Apple advisor, we got nowhere. We've tried everything. At the end he instructed me to force another update via PC. Unfortunately, it didn't work so I'll have to contact them again on Monday, as he told me to do so.
edit: after another 90 minutes of restarting and trying to set up the phone, it finally worked! About 15 minutes ago I accepted the terms and conditions on the iCloud page (I didn’t check if it was about Apple Intelligence), but the phone finally unlocked!!!