Yeah that's precisely the problem. NixOS also still supports i686 and it can still compile a lot of stuff (except afaik a lot of i686 specific build problems aren't actively being fixed), but there don't seem to be any prebuild packages for i686 atm.
I have really slow hardware (Pentium M 1,6GHz) and after 48h of compiling I decided that NixOS wasn't gonna work (at least without binary caches).