How to break my habit of folding legs on chair and hunchback?

>I have a regrettable habit of folding my legs on the chair when working and hunch back, which is unhealthy.

Nerd neck. https://www.youtube.com/watch?v=WIsx1t8TJq4

>Anyone who had struggled with something similar in the past, please share your advice and experience.

So here's the thing, my nerd neck was BAD. There are many other videos like this one. There's another trick of fixing your hip angles that will realign things which can help as well; but still effort being made. It's not going to be an instant fix but boy do you ever want to do this. It's a very bad decision to not go this direction. You need to fix your posture for your own sanity.

The thing that really helped me the most. Alexander technique.

https://www.youtube.com/watch?v=iriXg5uZ_oU

There is a spot where when you get aligned properly, you basically keep good posture automatically without thinking or any effort. In fact your muscles will suddenly relax for the first time in a long time and you'll never go back to bad posture. Alexander technique is lazy living, and yet practically perfect posture.

The other thing that will help greatly. Breath properly. When you breath properly, your lungs will put you in good order.

https://www.youtube.com/watch?v=ldNnKVGxabA

Incidentally, all of these things tend to lead to anxiety and adhd.

Before anything, make sure to root out any incentives for bad posture from your environment. Just like how tall people sometimes stoop to hear/see the people they're talking to, you may be hunching as a "solution" to some problem in your environment. If you don't fix those problems, any posture adjustments will be short lived.

Some low-hanging fruit there: Make sure your screen is at eye level (when sitting up straight.) Make sure the font sizes on your computer are big enough that you can read without moving your face closer to the screen.

Folding your legs is also going to lead you to hunch if you're not flexible enough to sit up straight while doing it. (I'd wager that most western adults aren't.) Make sure your chair is at a height where you can have your feet comfortably on the ground. If the height doesn't work for your desk, get something to put your feet on. (My wife uses a laundry basket.)

In case of a dire need for intervention, strap your feet into a snowboard while working. (Half joking, but with my own ADHD, I feel like I'd need to physically restrain myself to break a deeply ingrained habit like that.)

No matter what position your legs are in, it is the head and neck you need to align - make sure your screen is placed somewhere that makes you keep your head and neck up to look at it.

If you are working directly on a laptop, get an external keyboard. Disconnecting your screen position from your hand position can go a long way.

Build strong back muscles and core muscles. Do rowing movements like inverted bodyweight rows or maybe pullups if you can.

Standing desk?

What's your workout regime? Squats? Bench press?

Perhaps look into a "kneeling chair".

Are you working from home or in a workplace? Available options are much more limited with the latter.

it's not necessarily unhealthy

anyway try half lotus instead. instant pelvis realignment