Hello, I would like to ask if there is a way to make that Dynamp render all unknown block in black but opaque (non transparent).
In order that if a house is made from unknown blocks, players that see the dynmap online don't see the house's indoor.
Thank you in advance.

You could also see about adding support for the new blocks. https://github.com/webbukkit/dynmap/wiki/Custom-Block-Definitions

Yes, but if a house is build with unknown block, they should be opaque in dynmap, not transparent.
The problem is Chisel, these block are not rendered even with Dynmap Scan.

Maybe some of these will help you:

Dynmap Chisel 2 Config
Someone's render config for Chisel 2
https://github.com/Zehir/Dynmap-Chisel-2-Config

DynmapBlockScan ( not updated since 1.15.2, but if you can generate the block data on 1.15.2 it doesn't matter)
This might be what you referred to before, Client-mod that generates textures for missing blocks. You still need the render config above to tell dynmap how to map to the textures made by this
https://github.com/LolHens/DynmapBlockScan

More useful info
https://www.reddit.com/r/feedthebeast/comments/bwa5q6/how_to_dynmap_mod_textures/
https://github.com/webbukkit/dynmap/files/679635/chisel-models.txt
https://github.com/webbukkit/dynmap/files/679636/chisel-texture.txt

Is there a solution for Dynmap and Chisel on 1.12.2 ?
Even just rendering Chisel Blocks as black opaque would be fine, just not transparent please.