On godot 4.1, downloading a zip of the master branch and adding it to a fresh godot project I get:

Getting past that dialog and attempting to enable the plugin through the settings, we get the following error:

Unable to load addon script from path: 'res://addons/tbloader/src/plugin.gd'. This might be due to a code error in that script. Disabling the addon at 'res://addons/tbloader/plugin.cfg' to prevent further errors. 

taking a look in plugin.gd we have:

@krazyjakee I see that you've done a merge request with 4.1 recently, do you know of anyway we could fix this?