Unity 2019.3

Hi,
There is no file LocalizeTarget_UnityStandard_GUIText.cs in the current assetstore version of the I2 Localization.
In that release, I remove all the GUITexture, GUIText, etc from I2 Localization.

Be sure to download the latest version from inside unity 2019.3 so that it gets the appropriate package.
If after updating, you still have issues with GUIText, etc, it means that unity didn't remove in your local projects the files I deleted.

To fix this, delete the I2 folder and install the plugin again, that will remove all that is not needed and install a fresh copy of the plugin.

Hope that helps,
Frank

All your terms are stored in the I2Languages.asset which is stored in Assets\Resources.
If you delete the Assets/I2 folder, you still have all your terms, just open that asset and I2 Localization will recognize them.

If for some reason, you have 2 I2Languages.asset in different folders, just delete the one that doesn't have any term.

Hope that helps,
Frank