On Android, Pixel 6, version 2.0.00 snapshot 10-27
It takes like 5 seconds for every little action to resolve and every phase to change. This happens elsewhere if there's a complicated board state, etc, but Zedruu's Chef is slow even before the first land gets played.
I would assume his huge deck (250ish cards) has something to do with it, but the Soren boss has a similar sized deck and that doesn't get unbearably slow until later, so I have no idea what's going on.