Are there any implementations of the spineless tagless G-machine other than in GHC?
I used this Google search:

"spineless tagless g-machine" site:github.com


and found 2 repos that (try?) to implement the STG in non-Haskell languages:

PHP: lechimp-p/php-stg

RPython ("restricted" subset of Python developed for Pypy): cgswords/laurens