select your file, and then it’ll then give you a url which you would then just put in the url box of a post, or anywhere else you want to share an image. don’t use imgur, they don’t permit using it to share images to other sites, which is ironic considering they’re an image host but hey don’t ask me why they do that.
get an old dell latitude or thinkpad. They’re good performing laptops for the price you pay (somewhere around 50-100 usd) and the hardware’s old enough that any built in peripherals such as a microphone, webcam, or trackpad should just work. As for a distro, it depends. If you don’t want to learn anything or a bare minimum amount about your computer to use it, use linux mint*. If you want the freedom to turn your desktop into anything you want and don’t mind learning a thing or two, use arch.
*xfce will perform the best, but any version will work just fine.