OP, think about what percentage of your life you spend in various places (chair, bed, car) and invest accordingly, i.e. spend money on your bed and chair, these are life changing, low-cost investments
Here's the one I bought https://www.amazon.com/dp/B07XHBYY87
I'm certain there are even nicer ones out there but this one is great. Super comfy for long hours (I still code, LLM and manually, a lot) and I like being able to lean it back.
Oh yeah I also got this foot rest to go with it under the desk, which was a good choice as well