My feed won’t update for over 20 hours, and I have old feeds from yesterday in my Today folder. I’m on the latest TestFlight
Something similar happened to me also. I think the “producer” of these feeds made some changes, so these appear as “new”.
I made some tests with self-produced feeds and my experience was that, as soon as I have done some changes in existing feeds, these appear again as new feeds.
But maybe I am wrong, I am not an expert for RSS/feeds.
The Today feed shows articles from the last 24 hours, so it’s normal to have articles from yesterday.