Question Blending adjacent biomes rendered by a shader reading from several textures

Hi, I'm new to graphics.

I set up a shader graph assigning provinces' (each one a mesh) UVs to textures after reading from a bitmap. It works but it is already performance heavy.

How to blend said rendered textures in a simple and economical way (i.e. transition smoothly between biomes' textures and hide those squares)?

Thanks.