The ergonomics of working from a shared bedroom
Raise the screen to near eye level with a stand or books. Keep feet supported, elbows near a right angle, and the keyboard close enough that you do not reach. A pillow or lumbar cushion can improve an ordinary chair.
Change position often. Stand for calls, stretch between tasks, and pack away work equipment at day’s end. Do not use a bed as a full-time desk if you can avoid it; it blurs rest and work while straining your body.
The useful goal is less discomfort, not a perfect office chair in a tiny room.