A few of use users discussed this here: Request for Detailed LVGL Multilanguage Implementation Guide with SquareLine Studio (SLS)
I got it working just fine in Windows 11 by installing node.js, then following the Install/run the script from the lv_i18n github project. I ended up doing a local install of lv_i18n but from github’s repo master branch. A local install will lv_i18n into a subfolder of node_modules in your current directory from the command prompt. Then you can execute the lv_i18n commands in a command prompt like:
node_modules\.bin\lv_i18n extract -s "main/**/*.+(c|cpp|h|hpp)" -t "main/translations/*.yml"
node_modules\.bin\lv_i18n compile -t "main/translations/*.yml" -o "main/lv_i18n"
In these commands, my translations were inside main/translations folder, my source files were in main folder, and the lv_i18n folder was in main/lv_i18n.