I don't know about other EVs, but the Leaf shows the battery capacity on the dashboard at all times - if you know how to read it. I had to google it because the salesman had no idea.

The first leaf we looked at was already down to 80%, but the second was in perfect condition at two years old, and is still in perfect condition at age six.

https://cdn.motor1.com/images/mgl/Ke7gb/s3/leaf-state-of-cha...