with all the speak about linux still running on old hardware: yeah but there comes a point where it gets really painfull.
Linux is better in this regard but not perfect. Let me sing you a song of how I struggled to browse the web on a 1999 IBM Thinkpad T23 with a Pentium III CPU.
No modern browser supports that CPU. You can modify firefox with enough technical knowledge to run on that thing but... apart from some very simple text based browsers, no support for that CPU.