It’s x86-64 only. A quick look at the https://github.com/tenderlove/tenderjit/blob/main/lib/tender... linked from the README reveals heavy references to x86-64 registers. The “Fisk” library used appears to be a x86-64 assembler in Ruby.

I guess that’s to be expected with “pure ruby” — all the cross-insn backends you can use (Cranelift, LLVM) are written in not-Ruby.