Do rivers "block" adjacency of districts and wonders?

In Civilization 6, do rivers "block" adjacency of districts? Put another way, are two tiles with a river running between them "adjacent" for the purposes of district bonuses and placement restrictions?

The immediate context is that I think I should be able to build the Great Library on a tile across a river from my campus (pictured below), but the wonder does not appear for building. More remotely, I'd like to build a triangle or diamond of districts to maximize the adjacency bonus, and I want to know if a river running through will counteract that.

I've looked in the Civilopedia and on the various Civ6 wikis but haven't found a true definition of adjacency and particularly how rivers affect it.

Solution 1:

Rivers don't block adjacency bonuses. That would really mess up building cities, as river tiles are usually very valuable and essentially being forced to either give up adjacency bonuses or river tiles would be terrible design.

The Great Library (by the way, don't build it. It's a terrible wonder) needs a campus with a library in it. Does your campus have one? Also it needs to be built on flat land, not on a hill. Please share a screenshot of the situation, if you meet all those conditions. I can figure out why you can't build it with some visual help much better.

From your screenshot it doesn't look like the Library even was in your list of buildable wonders, wihch means somebody else already built it. If it is buildable, but no tile fulfills the requirements, it should appear grayed out like the pyramids in your screenshot. Otherwise it should have been a legal placement option.