Possibly "oak flake gall" - "The hairs are white at first but soon turn brown"

There is also a "woolly oak gall" that has a similar appearance.

Oh great! The hosts are both Bur and Swamp white oak (my only two oaks) :0)

I must've caught this new one early as it was so white and fluffy.

This year there were only a few of the galls I posted about last year In this thread

And there was only one leaf with the new galls in the picture above, so overall, the tree looks the best it's been so far. There was some leaf tatter early on but it was exceptionally dry early spring.

And so far, nothing has affected the first crop of 7 or 8 acorns at all. Not fully formed but definitely have the 'hairy' caps of Bur acorns.