Hello Trait74, sorry for keeping you waiting so long, and you may no longer need the answer, but I'll leave it here for anyone who sees this.
Blunder and BLUI are Application Templates, not addons, they won't show up in your addons list, they will show up in File > New > after you have installed them.
I don't recommend Blunder at this point, it's only there for archival purposes, BLUI is the template that has been updated most recently.
If you want to uninstall Blunder or BLUI the process is the same, and for now it is manual, unfortunately. I'll use BLUI as the example.
You will need to delete the following folders/files to remove the templates from your system:
~/YOURUSERNAME/AppData/Roaming/Blender Foundation/Blender/2.93/config/BLUI/
~/YOURUSERNAME/AppData/Roaming/Blender Foundation/Blender/2.93/scripts/startup/bl_app_templates_user/BLUI/
~/YOURUSERNAME/AppData/Roaming/Blender Foundation/Blender/2.93/presets/keyconfig/BLUI_keymap.py
And that's it, you're done.
From now on BLUI comes with an auto-installer that runs on startup, so the install process is much faster/easier, maybe I should add a fast/easy uninstaller, too.
Thanks!