Cool exploration, and very much needed because depressingly few people who use these engines actually understand this.

Back in 2021 I got cfish and weiss working on a 386sx, though didn't test it much. cfish was doing 5k nps so some results can be extrapolated. NNUE complicated things due to RAM requirements. Though I did train a small one for lichess at some point and they can be surprisingly good.

edit. A good view on the continuous progress of Stockfish itself https://nextchessmove.com/dev-builds