Easysubs is an open source app that allows you to download subtitles from OpenSubtitles in a very fast and simple way. I used electron-vue as a starter and Photon for the UI.
I was using a similar app that recently stopped being free.
$ git clone https://github.com/matiastucci/easysubs
$ cd easysubs
$ yarn # or npm install
$ yarn run dev # or npm run dev
$ yarn run build # or npm run build