How to orient normal maps on a landscape with triplanar mapping

Hello I’ve been trying to make a landscape material similar to this one https://www.artstation.com/artwork/1egBq
Basically I want to blend the rockface material with the rest of the material using the slope of the rockface, but my problem lies in calculating the angle, because I’m also using triplanar mapping, so the values of normal maps get all "tossed around

Here is an example, I circled in red an area where the angle if particularly noticeable.

I tried various techniques for the triplanar mapping, such as the included World Aligned Blend (both the complex version as the standalone normals version), then I tried this solution https://www.reddit.com/r/unrealengine/comments/70o0js/material_super_cheap_triplanar_mapping_solution/ and the triplanar node setup included here https://www.reddit.com/r/unrealengine/comments/eez7gf/free_unreal_engine_landscape_shader/

Sadly nothing made my normals align correctly, so I’m asking if anyone knows how I should approach this, I’m at a loss because I’m also not very familiar with the workings of computer graphics math and normals.
I’d also really appreciate it if my material would have a way of handling the blending of the projections, as shown in this pic from the 1st link from artstation I shared

And at last I’d also like to ask if anyone could explain or just share a node setup for biplanar mapping as seen here Inigo Quilez :: fractals, computer graphics, mathematics, shaders, demoscene and more since I feel it’d fit my needs

anyone can help me?

Lighting uses only a single normal. However, triplanar mapping has tangent space normals in more than one space. You can’t blend the normals “normally” – you have to transform each of the tangent space normals to a shared space, and THEN blend, and then provide it to lighting.
If you can’t do that, then you need to provide world-space normals in each of your maps (which means that you need six different normal maps for the six different sides) and blend them, and then invert from world space back into whatever space the lighting output wants.