2.5D Demo with GDScript Error

[AbydosRoad]

Which demo project is affected:
2.5D Demo with GDScript

OS/device including version:
Kubuntu 24.04

Issue description:
I searched the issues here in the Godot Github, but could not find an existing bug report on this issue. Upon opening the 2.5D Demo with GDScript for the second time (to ensure all of the assets were properly imported), I got the error: res://addons/node25d/node25d_plugin.gd:13 - Invalid call. Nonexistent function 'get_editor_viewport' in base 'EditorInterface'
I opened the indicated script and found line 13 as indicated in the error, there were no errors indicated in the code. I understand that this demo was created in Godot 4.1, I am running Godot 4.3.stable. I am fairly new to Godot and GDScript, but I do have a background in other OOP languages: C# and VB.NET. Thank you for your time!

Screenshots of issue:

[AbydosRoad]

Update: In looking further into the code, I suspect that at least part of the problem may be due to the 'get_editor_viewport' was incorrect, and should have been 'get_editor_viewport2d', as this looks to be a Node2D. Changing that removed that error, however, two new errors came up:

The second error runs non-stop with the project open, but not running. I am afraid my current level of GDScript knowledge is insufficient to troubleshoot this further. If you have any ideas or code changes you would like me to make, I would be happy to implement them. Thanks!