If what you want is a used laptop id look into the Lenovo Thinkpad T480, or Dell Latitude 7400. Both have great linux support, are very repairable, and upgradable, and personally i own a 7400 and love it. You can pick either up for around 200$ and spend the rest upgrading them. The thinkpad one is gonna be a bit slower probably, and a bit less slim, but will have better thermals, and battery life most likely too. The 7400 for me required a good bit of tweaking to get it running nicely. i added some thermal pads, repasted cpu, flashed bios update, and did some software tweaks to get thermals under control. If your not up for that the T480 has a massive fanbase online to help with any issues. Careful when looking at options that you dont go for the cheap screen. Get a 1080p screen option one youll regret it if you get the shit screen.