https://www.debian.org/releases/trixie/release-notes/issues.html#reduced-support-for-i386
From trixie, i386 is no longer supported as a regular architecture: there is no official kernel and no Debian installer for i386 systems
[…]
Users running i386 systems should not upgrade to trixie. Instead, Debian recommends either reinstalling them as amd64, where possible, or retiring the hardware.


but the debian i386 architecture means all 32 bit x86 processors. there’s no “i686” build of debian
there are no i586 or i686 kernel or iso available, you can look for them. i386 packages only exist for compatibility reasons, so you can run 32 bit applications on amd64 machines. please read the release notes