Part of the problem is that LLVM developers themselves are apparently unwilling to release support for architectures that they see as liable to go unmaintained and bitrot in the future, even if someone shows up and does the work. There is a notion of "experimental arch's" but it doesn't seem to be actively used, or to suffice in addressing the issue.
Experimental archs were just used recently for wasm and riscv to find maturity.
Are you referring to a specific discussion on the llvm-dev list? Last one that had a discussion in this area that I recall was Nios2.