It's pretty straight forward... Download the FBX2glTF tool and unitypackage_util tool from github.
The unitypackage_godot starter project puts things into a folder called imports
by default and isn't perfect with scenes.
The unidot_importer is a godot addon that should be placed under a folder in your godot project called addons
. It appears to be better with scenes, but requires the modded FBX2glTF tool.
https://www.youtube.com/watch?v=N3oWEBRv9SE
https://gamefromscratch.com/move-from-unity-to-godot-engine-in-seconds/
git clone https://github.com/barcoderdev/unitypackage_godot.git
cd unitypackage_godot
mkdir addons
git clone https://github.com/V-Sekai/unidot_importer.git unidot
Then to use Unidot, enable it then find it under tools.
Project > Settings > Plugins (tab) > Unidot Importer > Enable
Editor > Configure FBXImporter... > (Change path to FBX2glTF.exe location, should be root of your project)
Project > Tools > Import UnityPackage
Also all of your current unitypackage files from the unity asset store live here:
%APPDATA%\Unity\Asset Store-5.x
or
C:\Users\username\AppData\Roaming\Unity\Asset Store-5.x\AssetProvider\AssetName\abc.unitypackage
https://github.com/ProjectUnifree/unifree
Looks promising
https://www.reddit.com/r/godot/comments/143i3dl/tip_how_to_import_unity_prefabs_with_animations/