Well, this is one of the few times that Blender NOT crashing is letting me down. I can't reproduce the 2.91.2 crash on my system, it just loads the startup scene and waits, like it should.
My new theory is that there's maybe an initial setting that I had set when I installed 2.91.0 that got copied over to my 2.91.2 install, and maybe you don't have that preference? It's a bit of a weak theory, but it's all I've got right now.
When I installed Blender, and opened it for the first time, it showed that one-time pop-up that asks you if you want to use Left or Right Click to select, and if you want to load the Blender default or Industry Standard Keymap. I believe that I chose Left Click and Industry Standard. You could try changing these settings first, then going to File > New > BLUI.
Really, I'm not feeling confident that this will make a difference, but it's something to try.
I'll try to modify the Blunder init script to see if that makes a difference.
Thanks for the interest, and patience, there's been a few people lately after me to update and maintain my addons/templates, and I think that was just the kick in the butt I needed to get cracking again. Hopefully I'll have some updates to share with you soon.
And, as far as the Blender Python API is concerned, I agree, the docs seem to be missing that last critical step, maybe just an example of the syntax needed to use each of the operators. I'd also been meaning to do a video on how I make all my stuff, including resources that helped me get from where you are with it, to where I am (which is not all that far, but I remember thinking the thing you wrote). So I'll leave some of those resources here for you to check out, and there'll be a video about it on my Youtube eventually:
Blender Python Getting Started:
Darkfall - https://www.youtube.com/channel/UCOUWVGNhcHEICE8AjR8up3g
B3D Interplanetary - https://b3d.interplanety.org/en/
Curtis Holt - https://www.youtube.com/channel/UCzghqpGuEmk4YdVewxA79GA
Jayanam - https://www.youtube.com/user/jayanamgames
Scripting for Artists (on Blender's official YT channel) - https://www.youtube.com/playlist?list=PLa1F2ddGya_8acrgoQr1fTeIuQtkSd6BW
Royal Skies LLC -
CG Matter -Blender Livestreams - they did a stream with the guy (Dr Sybren Stuvel) who did the Scripting for Artists series, and I asked a few questions about REALLY basic stuff, then I started to feel bad that I should have maybe Googled it instead of wasting his time, but when I went back to the comments, he had gone back after the stream ended and written a detailed explanation that really helped things click for me.
Royal Skies and CG Matter helped remove that intimidation barrier I felt whenever I looked at the API - Hey, just do the things you want to do, copy and paste them from the Info screen, and BOOM, you're a coder.
Darkfall and Nikita are really good at going through code line by line, or section by section, and making sure you understand how it all works, they were the ones who helped "connect the dots" and allowed me to figure out how to actually write out the things I wanted to do.
All the others helped me get that one tiny little piece that someone else thought went without saying.
Once you're up and running, your new home will be https://blender.stackexchange.com/
That's the best resource I've found for Blender and Python.
You can also try reading through my scripts on Github, I ignored a couple of "Python style" recommendations, like abbreviated variable names, and 80 character lines, so all of my variables are super long, literal names (eg a variable containing an Object's coordinates would be ObjectCoordinates, rather than objco) and I've put in lots of comments, to try and give the plain English of what each code block does right above the code itself.
Damn, I wrote a novel, and I still didn't fix the crash! I'll keep you posted!