This looks like classic cicada egg-laying damage. They utilize a wide range of tree species, though oak is either a favorite or one on which the damage is more prominent. As we experience more stormy weather this summer and autumn, these twigs will snap off. It's a natural pruning process which actually benefits the trees in the long-term.

The tiny cicada eggs are wedged into the slits on these twigs, and they will hatch in another several weeks. Their root feeding for the next 17 years is also minor and will not damage plants.

Here is more information on their behavior, plus images you can compare to fallen or browned twigs you encounter:
https://extension.umd.edu/resource/cicadas

https://cicadacrewumd.weebly.com/gallery.html (see "damage to plants" section)

If you see symptoms of dieback that doesn't seem to be correlated with egg-laying damage (that is, you don't see any slits in the stem), feel free to submit photos for diagnosis. In that case, images showing where the dying branch meets healthy growth are the most useful. In cases where trees are too large for good images and inspection, we recommend contacting an arborist.

Miri