Several years ago (Maybe around 2014?), I set up an old Toshiba Satellite Pro 4600 laptop, just to see how usable it was. It had a 1024x768 LCD panel, a Pentium III, and 128MB of RAM - which I upgraded to 512MB. I used the stock mechanical HDD, although in retrospect I think an IDE-to-CF adapter is the way to go (IDE-to-SD adapters exist, but they are slower than a decent CF card).

My memory is a bit fuzzy, but I was able to install Lubuntu with LXDE (or maybe it was some other distro with LXDE?), and browse the modern web with Chromium - albeit painfully slowly. Around 15 seconds to load bare-bones pages like HN. I guess it was swapping to disk...

I did test Firefox too, but it performed worse than Chromium.

Lubuntu has changed their goals a bit since then, so YMMV if you wish to use it today:

https://lubuntu.me/taking-a-new-direction/

"we will no longer primarily focus on older hardware"

It's sad to see them change course, but I don't blame them.