Linux

Firstly, yes, what OP wants is absolutely feasible in principle. I've used fanless low-powered laptops as my only device for years now, for same use case as OP - terminal plus browser. First was an 11in Asus netbook, right now a Celeron-powered model with fully 8GB ram. Neither have been "slow" at all, in fact probably faster than some of the Windows machines I've used in the past for work. HD video runs flawlessly, which is as much as I'll ever need. For both of them I paid as little as you'd expect - in the low hundreds, new. To be honest I often get the feeling many people are buying super overpowered laptops. If you're on Linux and not gaming or doing CAD it's a complete waste of money to spend 1000 bucks on a laptop. That's my opinion, backed by very deep experience.

In response to the question, the problem is that the netbook niche is now occupied by Chromebooks. Which are a PITA to get working with Linux due to the bootloader lockdown - although OP seems to have the secret for making that easy. Otherwise you need to go up to around 350 bucks for the lowest-end Wintel devices which are not bulky with horrible fans, or else buy second-hand as others are recommending.