Lots of good technical starting points here. I don't want to prematurely discourage you, but before you get into any code, evaluate your problem solving abilities. If that is an area you struggle in, work on that first, or at least in conjunction with programming basics.
I've worked with engineers who have all the code skills, but when faced with a complex issue, struggled to break it down into it's simplest components and wound up with a messy, over-engineered solution.
My social anxiety would love to give a one word answer and move on, my ADHD/self-doubt/trauma says "are you sure that's enough? they'll think you are an idiot and don't know what you're doing if you don't elaborate"
This isn't an endorsement for brave, but the websites aren't loading properly because they are full of the trash that brave blocks, not due to bugs in the browser.
For me, it depends on how much time I have before starting. If the start is immediate, "I'll figure this out on the fly" then ride that "oh, shit I don't know what I'm doing" adrenaline fueled dopamine wave all the way to borderline success. If I have lots of time before starting I'll over analyze then try and fail to become an expert and give up before starting.
Echoing what others have said, get the meds. I'm 39 and have been taking Vyvanse for a couple years; when I forget I am a mess, I can't believe I made it this far without.
I've been working on this lately, what I find helpful is reminding myself that the chore doesn't have to be done perfectly, and that some progress is better than no progress. I struggle with perfectionism and will put off tasks indefinitely because of fear that if I start wrong or don't finish it immediately it won't be perfect. My therapist helped me to realize that perfect is the enemy of done, and that it is ok if something isn't done perfectly.
The bulk of my day to day work is with a legacy application written in vb.net, and I couldn't agree more with your first paragraph.
I feel like I'm too senior to ask this, and should know better, but my main responsibility is a .net framework 4.8 application, so I may have missed a memo. Why does Newtonsoft.Json need to be stopped?
Sounds a lot like hyper-focus to me too, but like most traits shared by ADHD and Autism, there are probably some subtle differences. Personally I find the inertia terminology to be more representative of my experience.