For a old laptop with Intel atom processor and I think 2gb ram.
Also, I’ll just mention that it all means nothing as soon as you open a browser window. Then all your RAM is gonna be used up anyway.
Can I introduce you to Lynx?
Sure, play your youtube videos on Lynx.
We all know that’s one of the main things people use browsers for, that’s not work, these days. ;)
Downloading videos via yt-dlp and playing via MPV will not take all the RAM. And Firefox with uBlock Origin can be set to hard mode to block scripts, or even nightmare mode for a barebones no JS experience.
Lubuntu. Do not bother with anything else if you want easy to use solution. You could use LXQt with Debian if you are advanced, but it will lack a lot of the polish that Lubuntu will give with networking/WiFi related things.