I mentioned elswewhere, but Apple started selling 32 bit Core (not Core 2) MacBook Pros in 2006. Those seemed dated even at the time. I’d call them basically the last of the 32 bit premium computers from a major vendor.

Frankly, anything older than that sucks so much power per unit of work that I wouldn’t want to use them for anything other than a space heater.

Intel Prescott, so like 2004.

For what it's worth, people may have been running 64-bit CPUs, but many were still on 32-bit OSes. I was on 32-bit XP until I upgraded to 64-bit Win7.

I have to imagine that group to be pretty small by now, though. Most PCs with specs good enough to still be useful now run W7 64-bit about as well as they do XP SP3 (an old C2D box of mine feels great under 7, as an anecdote), and for those who’ve been running Linux on these boxes there’s not really much reason to go for a 32-bit build over a 64-bit one.

You forgot to mention RAM. Old PCs have often <=4GB RAM and 32-bit browsers use less RAM: https://www.ghacks.net/2016/01/03/32-bit-vs-64-bit-browsers-...