Updating your discussion with the ‘Godot Help’ tag

Nikolay godot has its own tool for fbx -> gtlf conversion: https://github.com/godotengine/FBX2glTF

Download it and stick it in the path.

edit: if you fancy running it manually, the engine runs it like so:

.\FBX2glTF.exe --pbr-metallic-roughness --input .\your_model.fbx --binary

a year later

Nikolay
Hello! Could you please tell me how you managed to solve the problem?

    3 months later

    Bitgy

    I know it's late to reply to this, but in case it's still helpful...you first need to download rust.
    Pretty simple to do, you can open any terminal and copy and paste the curl command the site provides.

    Once you have rust installed, you can clone the util repo from barcoderdev.

    Next open a terminal from the root directory of the cloned repo (unitypackage_util/) and then run the following command...
    cargo run

    The run will fail and you will be prompted to view the terms of the xcodebuild license. so enter (as prompted)...
    sudo xcodebuild -license

    ...and press Enter to view the license.

    Next type agree

    When that is done, again run...
    cargo run

    ...and it will build the util executable. You will find it in...
    unitypackage_util/target/debug/

    Hope that helps.