I’ve been able to run AntiX on my Pentium 3 rig, and it was significantly faster than Windows XP. AntiX is just Debian meant to run on very low end systems. I’m sure an Athlon 64 X2 could easilly handle something like Xfce or LXQT. The main limiting factor is going to be the system RAM.
Modern Linux with a light-weight DE would work pretty well, too.
Looking at the Geekbench 6 scores for the top end Athlon 64 X2 (I definitely did not have a 6000), you would need a really lightweight DE.
I’ve been able to run AntiX on my Pentium 3 rig, and it was significantly faster than Windows XP. AntiX is just Debian meant to run on very low end systems. I’m sure an Athlon 64 X2 could easilly handle something like Xfce or LXQT. The main limiting factor is going to be the system RAM.