I have actually upgraded a really old 32 bit only laptop from bookworm to trixie - it works. Two important (for the desktop environment) packages required SSE3 which the CPU doesn't support, so... I installed package "sse3-support" with environment variable IGNORE_ISA=1 set. The kernel was not upgraded because trixie doesn't contain an i386 kernel. The laptop works surprisingly okay, though of course it's not much fun with its weak performance, low RAM and mechanical disk.