Legibility means, to the best of my knowledge, that the handwriting or printing is easily read.
Is there an equivalent meaning for ease of reading? That something is written in a way that the reader can easily understand the content?
“Intelligibility,” or “comprehensibility.”
“Clarity” is often used to express this concept, although of course that word can have other meanings also.
“Readability”?
No. Note the prominence of optical qualities there.
But it is still called readability.
It is, but the word is not precisely and specifically that; it can include elements overlapping with “legibility,” from which the OP sought to distinguish.
Yes, there’s a difference. Legibility generally emphasizes how easy it is to identify letters, punctuation, spacing, etc., and usually involves things like font, font size, spacing, margins, etc. Readability is about comprehension of a written document whose letters, spacing, and punctuation have already been identified. It involves things like complexity of vocabulary (e.g. is it full of technical jargon, archaic verbiage, or very long words), and the use of convoluted grammar, subordinate clauses, long sentences (as opposed to multiple short sentences), etc.
Here’s a simple example:
Low readability:
It is meet that we embark upon a new and courageous journey toward the heavens, where we will bask in the beauty of foreign spheres. Though our spacecraft engineering process will last upwards of a decade, we are confident that our specialists will achieve the appropriate propulsion-related goals.
High readability:
We need to do something new and brave. We have to go into space and visit other planets. Those planets will be beautiful. It will take at least ten years to build a ship to do this. We have people who can build the right engines.