None. The yellow-ish screenshot was on something called Slitaz. It doesn’t exist anymore but that OS was phenomenal. I actually bought a very old pc with only 512 ram just to see what that OS could run on. Believe it or not, it still was very fast. I ran chromium on that thing if I recall correctly. I modified the lxde iso to run openbox and tint2 only. It actually booted at 28 Mb ( even Puppy linux was a lot heavier). But, it’s no longer available. But no, I doubt you can run a modern browser with only 512 Mb. Not even on something like Antix or a Debian minimal. That other screenshot was a debian minimal, a setup from scratch with 2 Gigs I believe. FF hovered around 1 Gig-ish on that one. It’s all desktop specific. There’s, for example, already a big difference in a standard, say, Debian iso and a minimal. The ram usage for a browser will differ on those.
Debian minimal/openbox/tint2/Rox desktop:
“Default” Sparky ( Debian-based)LXQT iso ( one ssb running)
Default MX ( Debian), xfce with openbox wm, firefox running:
So, I’d say that in order to have a functional modern browser running properly, you’d need 2 Gigs of ram on a lightweight system ( unless you have something exceptional like RIP Slitaz)