If “Screen Unknown Senders” stops working for Messages in iOS26
This happened to me on my iPhone SE 3 running iOS 26, and I found a simple fix at https://www.reddit.com/r/iphone/comments/1nlbq4r/comment/nlqahws/: turn off "Screen Unknown Senders", shut down the phone completely, restart the phone, turn "Screen Unknown Senders" back on.
This actually worked for me. Even previous SMSes from unknown senders that had not been filtered out of my main SMS list (and which had triggered annoying notifications, so that someone I didn't know could interrupt my Friday night to address me by name and ask me to reply indicating my support for a racist politician) suddenly disappeared from the main list and moved to the unknown senders list.
So, appears to work.

So, I had a crazy problem. You'll notice that there's various draggable elements on this site... such as the "Kupietools" plugin tabs seen at left, the occasional "the site is being worked on right now" notices that pop up, etc. You can drag them around with your mouse.