Debian Dropping Its 32-bit MIPS Little Endian "mipsel" Port
Debian 12 "Bookworm" is the last of the line supporting the MIPS little-endian architecture. MIPSEL is now removed from Debian unstable/experimental moving forward. MIPSEL had been one of the oldest architectures remaining in Debian with only i386 being older and now AMD64 the second oldest.
The justification for Debian dropping the MIPS little-endian architecture is due to the Year 2038 "Y2038" problem unresolved there, the 2G user-space memory limit, and lack of manpower on part of the Debian developers for maintaining the architecture. As such it's being dropped from the official Debian release architectures while MIPS64EL as the 64-bit little-endian variant will continue to be maintained.
MIPSEL being removed from Debian unstable/experimental was also announced today on the mailing list.
MIPS 32-bit CPUs can be found in old consumer routers and other embedded devices.
Those still running 32-bit MIPS little-endian are likely doing so on old embedded devices like routers and as such also not likely to be updating to newer Debian releases so frequently, if at all. Thus dropping it now from experimental/testing after the recent Debian 12 release makes sense given the lack of developer resources and other mentioned technical limitations.