My fix-actions originally took care of this problem, and I've been nag-free for over 4 months. (My fixes are listed in the post dated 16 Dec 2024.) Then, about a week ago, the nag banner came back, so, I came back here looking for any new ideas. It turns out, no one has any news ideas.
I went back through all of the fixes that were previously recommended, starting with Page 1 of this thread. When I got to my own post (dated 16 Dec 2024), I rechecked all of my settings, and found some of my work had been undone, probably by a MS update.
If you had success using the fix "uncheck the Microsoft Experience option in Account", go check it now... mine was re-enabled. I've unchecked it again. All of my other fixes were still in place. The "enable MS Experience" was the only one re-enabled which points directly to an update.