> On my computer it started in Dark Mode, and the experience overall was quite a bit disorientating. Also no light/mode switch icon in the header.
I don't really know that you need a light/dark mode switch. It should follow your preferences. I see dark mode websites all the time, because my desktop is set to dark mode. On my Windows machine I see the same websites with the light-mode, because I did not bother to figure out how to set Windows to dark-mode.
[EDIT: The Plane App ignores my preferences].