Not sure if that’s your case as well, but I remember that there was an issue with Intel Bay Trail tablets where the BIOS/UEFI was 32bit but the CPU could support 64bit OS just fine. You just need to get a special bootloader that will boot 64bit Linux kernel from a 32bit UEFI (which is not normally supported)

Here’s one reference https://github.com/dmotte/misc/blob/main/knowledge/linux-x64-grub-uefi-32bit/README.md - it should be possible for you to use a 64bit Debian, but you’ll need to get your hands dirty.

Hey, just a tiny note: static and dynamic addresses aren’t mutually exclusive. You can let SLAAC do its thing AND also set a static address on your server. Remember, IPv6 works best when you aren’t afraid of adding more addresses.