This question was inspired by comments on this question: "Does the mantle of the eyes extend your vision while on the etheric planes?"
Page 48 of the DMG states:
The ethereal plane is a foggy and nebulous dimension …
Visibility on the ethereal border It is limited to 60 feet. The depths of the plane comprise a region of mist and mist called Deep Ethereal, where visibility is limited to 30 feet.
It says nothing about visibility. inside the ethereal edge or deep ethereal.
the see invisibility spell states:
While it lasts, you will see invisible creatures and objects as if they were visible, and you can see inside the ethereal plane…
However, it does not establish how far in the ethereal plane it can be seen unlike any other method that you can find (the tunic of the eyes, the See true spell, even monsters with Truesight).
How much of the ethereal plane does see invisibility lets you see