The C4 compiler [https://github.com/rswier/c4] is a self-hosting compiler for a subset of the C programming language that produces executable x86 code. You can understand and audit this code in a couple of hours (its 528 lines).
It could be an interesting exercise to bootstrap up from something like this to a working linux environment based solely on source code compilation : no binary inputs. Of course a full linux environment has way too much source code for one person or team to audit, but at least it rules out RoTT style binary compiler contamination.
c4 - C in four functions: https://github.com/rswier/c4/
c4x86 - JIT compiler for x86 in 86 lines: https://github.com/EarlGray/c4
I was surprised to see nodes still have two pointers ("references") given that you now know that that the first pointer will always point exactly to the next node. I've see https://github.com/rswier/c4 use that. Granted it doesn't make for the most readable code, but it's even smaller and faster.
C4 comes to mind (C in 4 functions), https://github.com/rswier/c4.
have you considered adding a backend for LLVM? perhaps a bit heavyweight, but it could be a good way to get C/C++, fortran, rust, etc. if that's something you'd like!