The current 12.1 series free version does work on XP SP3 32 bit machines.
That is not entirely correct.
It only works if the CPU supports the SSE-2 instruction set.
The entire 2016.x version series will not work if a system doesn't support it.
Kinda the same is with the avast for business cloud version.
Only if you run the online installer it will work on non SSE-2 system.
The full installer doesn't work.