Shader Graph texture limit?

How many individual textures can you supply to an HDRP Lit shader made with Shader Graph?

And I am explicitly excluding texture arrays.

More info:
My game world is made of 72 tiles.
I use a lookup texture to handle game logic and some shading. One of the values it looks for is water, which is a large part of the game world. Since the entire texture is black (in the case of water) and has no game logic value, to save gigabytes of (V)RAM, I can split up the game world further and further to omit as many purely black textures as possible.
I can do that with textures easily (programatically), but splitting up meshes is not as trivial and it would increase the draw calls dramatically, aswell as reducing the amount of saved (V)RAM, since it would introduce new (duplicated) edges.
As an absolute minimum I need to be able to supply up to 64 textures to a shader, or think about splitting up meshes.

Additionally, if anybody has a different optimization approch, I’m all yours.

I don’t know about any hard limit (there may well be one though) but using that many textures is a bad idea for other reasons. Sampling textures takes time and you would always sample all textures in the graph, even if only one has an effect on the result. Try using a single Texture 2D Array instead where each element is one of the tiles. That way you only need to sample once and you can have as many textures as you like.

Edit: Here is an example shader graph for building a world from tiles. The world texture contains one pixel per tile that is then used as an index for the texture array. The texture array contains the actual tiles. Make sure that the world texture is set to point sampling (not bilinear).
Example graph
(I had to do it via Google Drive because somehow the picture upload isn’t working. Hope this works for you)