A modern version of Opera for i386 linux has been released.

It runs fine on an old AMD Sempron (circa 2010) and even plays embedded HTML5 YouTube videos fairly smoothly.

Ad blocking and a free VPN are built into it.

http://www.opera.com/blogs/desktop/2016/10/86-percent-faster-opera-41-for-computers

I've tried it on a few "Designed for Windows XP" machines and the only trouble I've had is with a few of the less common graphics accelerators, but you can turn off the acceleration features.

One gigabyte memory helps, which may be an upgrade from the 500 megabytes that was common at the time. Old DDR and DDR2 memory is often less than $5 a gigabyte on Amazon and similar places.

The Old Opera 12 was designed for such machines but it was having trouble correctly rendering some modern web sites.

Surprisingly, the modern Opera is less poky than the Chrome browser, even though it's using the basic Chromium engine.

I haven't tried it on Windows. It says it wants Windows 7 or later. I don't currently have any Windows machines, but I never know when I'll find one on the curb with a "free" sign on it, or in a dumpster. I usually won't do Windows unless someone is paying me.

I've got Opera running on Debian with LXDE, so it should be happy on Lubuntu.

Opera was my main browser since version 3, when it fit on a single 3.5" floppy disk and cost $35. A couple of years ago I switched to Chrome, mostly because Opera 12 was no longer loading images from some photo sharing sites. People would post pictures here on DU and I couldn't see them. With this new linux version it looks like I'll be returning to Opera.

I thought this would be helpful for anyone who doesn't buy a new computer every few years.

The last "new" computer I bought was a shopworn 386SX. Since then I've been using computers other people have abandoned.