Unable to load addon script from path

[123clover]

(this shows if i try to enable it)

Unable to load addon script from path: 'res://addons/Terrain3D-main/project/addons/terrain_3d/editor/editor.gd'. This might be due to a code error in that script.
Disabling the addon at 'res://addons/Terrain3D-main/project/addons/terrain_3d/plugin.cfg' to prevent further errors.

(this shows inside Output box)

  platform/linuxbsd/x11/display_server_x11.cpp:5260 - XCreateIC couldn't create wd.xic
  platform/linuxbsd/x11/display_server_x11.cpp:5260 - XCreateIC couldn't create wd.xic
  platform/linuxbsd/x11/display_server_x11.cpp:5260 - XCreateIC couldn't create wd.xic
  res://addons/Terrain3D-main/project/addons/terrain_3d/editor/editor.gd:7 - Parse Error: Preload file "res://addons/terrain_3d/editor/components/ui.gd" does not exist.
  res://addons/Terrain3D-main/project/addons/terrain_3d/editor/editor.gd:7 - Parse Error: Could not resolve type for constant "UI".
  res://addons/Terrain3D-main/project/addons/terrain_3d/editor/editor.gd:8 - Parse Error: Preload file "res://addons/terrain_3d/editor/components/region_gizmo.gd" does not exist.
  res://addons/Terrain3D-main/project/addons/terrain_3d/editor/editor.gd:8 - Parse Error: Could not resolve type for constant "RegionGizmo".
  res://addons/Terrain3D-main/project/addons/terrain_3d/editor/editor.gd:9 - Parse Error: Preload file "res://addons/terrain_3d/editor/components/surface_list.gd" does not exist.
  res://addons/Terrain3D-main/project/addons/terrain_3d/editor/editor.gd:9 - Parse Error: Could not resolve type for constant "SurfaceList".
  res://addons/Terrain3D-main/project/addons/terrain_3d/editor/editor.gd:11 - Parse Error: Could not find type "Terrain3D" in the current scope.
  res://addons/Terrain3D-main/project/addons/terrain_3d/editor/editor.gd:16 - Parse Error: Could not find type "Terrain3DEditor" in the current scope.
  res://addons/Terrain3D-main/project/addons/terrain_3d/editor/editor.gd:18 - Parse Error: "SurfaceList" is a constant but does not contain a type.
  res://addons/Terrain3D-main/project/addons/terrain_3d/editor/editor.gd:21 - Parse Error: "RegionGizmo" is a constant but does not contain a type.
  res://addons/Terrain3D-main/project/addons/terrain_3d/editor/editor.gd:27 - Parse Error: Identifier "Terrain3DEditor" not declared in the current scope.
  res://addons/Terrain3D-main/project/addons/terrain_3d/editor/editor.gd:52 - Parse Error: Could not find type "Terrain3D" in the current scope.
  res://addons/Terrain3D-main/project/addons/terrain_3d/editor/editor.gd:59 - Parse Error: Could not find type "Terrain3D" in the current scope.
  res://addons/Terrain3D-main/project/addons/terrain_3d/editor/editor.gd:128 - Parse Error: Could not find type "Terrain3DEditor" in the current scope.
  res://addons/Terrain3D-main/project/addons/terrain_3d/editor/editor.gd:130 - Parse Error: Identifier "Terrain3DEditor" not declared in the current scope.
  res://addons/Terrain3D-main/project/addons/terrain_3d/editor/editor.gd:133 - Parse Error: Identifier "Terrain3DEditor" not declared in the current scope.
  res://addons/Terrain3D-main/project/addons/terrain_3d/editor/editor.gd:134 - Parse Error: Identifier "Terrain3DStorage" not declared in the current scope.
  res://addons/Terrain3D-main/project/addons/terrain_3d/editor/editor.gd:135 - Parse Error: Identifier "Terrain3DEditor" not declared in the current scope.
  res://addons/Terrain3D-main/project/addons/terrain_3d/editor/editor.gd:136 - Parse Error: Identifier "Terrain3DStorage" not declared in the current scope.
  res://addons/Terrain3D-main/project/addons/terrain_3d/editor/editor.gd:137 - Parse Error: Identifier "Terrain3DEditor" not declared in the current scope.
  res://addons/Terrain3D-main/project/addons/terrain_3d/editor/editor.gd:143 - Parse Error: Identifier "Terrain3DEditor" not declared in the current scope.
  res://addons/Terrain3D-main/project/addons/terrain_3d/editor/editor.gd:147 - Parse Error: Identifier "Terrain3DEditor" not declared in the current scope.
  res://addons/Terrain3D-main/project/addons/terrain_3d/editor/editor.gd:151 - Parse Error: Identifier "Terrain3DEditor" not declared in the current scope.
  res://addons/Terrain3D-main/project/addons/terrain_3d/editor/editor.gd:152 - Parse Error: Identifier "Terrain3DEditor" not declared in the current scope.
  res://addons/Terrain3D-main/project/addons/terrain_3d/editor/editor.gd:168 - Parse Error: Identifier "Terrain3DEditor" not declared in the current scope.
  res://addons/Terrain3D-main/project/addons/terrain_3d/editor/editor.gd:188 - Parse Error: Could not find type "Terrain3DSurface" in the current scope.
  res://addons/Terrain3D-main/project/addons/terrain_3d/editor/editor.gd:200 - Parse Error: Identifier "Terrain3DEditor" not declared in the current scope.
  res://addons/Terrain3D-main/project/addons/terrain_3d/editor/editor.gd:201 - Parse Error: Identifier "Terrain3DEditor" not declared in the current scope.
  platform/linuxbsd/x11/display_server_x11.cpp:5260 - XCreateIC couldn't create wd.xic

(i'm using godot 4.1.1 stable flathub[bd6af8e0e] on linux mint os)
(i'm using Terrain3d version 0.8.2-alpha , Author Roope Palmroos & cory Petkobsek)

[TokisanGames]

Parse Error: Preload file "res://addons/terrain_3d/editor/components/ui.gd" does not exist.

It says right in the error messages that the files do not exist. You didn't install the plugin properly. Review the instructions and review your file system compared to the file names in these logs. If the files don't exist where it's looking, it will never work. That's obvious isn't it?

It shows right in your title that you installed it in the wrong directory.

res://addons/Terrain3D-main/project/addons/terrain_3d/editor/editor.gd'

Also use your console, not the output window. If you're a Linux user, surely you know how to open a terminal and run Godot through it.

Finally when posting code or error message, encase the content between lines with three back ticks. no slashes

\`\`\`
So it looks like this. 
\`\`\`

[TokisanGames]

Closing since the error message shows the addon was placed in the wrong directory, and no further response.

[TokisanGames]

Also mention of Terrain3D-main suggests what was downloaded was the code repository. If that's the case, you need to compile it yourself. If you wanted to download the binary file you need to do so from here https://github.com/TokisanGames/Terrain3D/releases as stated in the instructions.