Desk
“I’ll work from my couch.” Don’t. You’ll need your body long after you’ve retired. Don’t break it while you’re young. Our bodies are made for moving, not for sitting down for many hours, for many decades. I’m not an ergonomics expert, but I’ve learned a bit about it over the years. Working from the couch puts your body in a position that’s not good for your back and your hands.
Any office desk should work just fine. Bonus points for desks with adjustable height, so you can alternate between sitting and standing. I know IKEA has a few of those.
Chair
“I’ll work from the kitchen.” Don’t. It’s probably better than the couch, but you’ll be sitting down for many hours, for many years. Kitchen chairs are not made for that. Invest in a good chair. I have SpinaliS HACKER for a decade or so. I don’t know how available they are globally.