Tinyscheme is, like the name suggests, a small implementation of scheme. https://tinyscheme.sourceforge.net/ Compiled without debug flags, its way smaller than 180kb
gcc -DSUN_DL=1 -DUSE_DL=1 -DUSE_MATH=1 -DUSE_ASCII_NAMES=0 -Os -fpic -pedantic -I. -Wno-char-subscripts scheme.c dynload.c -o scheme
There is also SectorLISP which is absolutely tiny, but more basic https://justine.lol/sectorlisp2/
SectorLisp is a lot of fun. Thank you! Those will take some time to build for all the platforms, but I will get there!