Automatically sync local books to your Kobo by pretending to be the Kobo Store
On the Kobo, open /.kobo/Kobo/Kobo eReader.conf and change api_endpoint to your local machine where Kobink runs (e.g., http://192.168.0.1:3000). By default, Kobink runs on port 3000.
Install dependencies and run:
LIBRARY_PATH=/path/to/epubs cargo run
Press "Sync" on the Kobo — all EPUB files in LIBRARY_PATH should now automatically be fetched to the device.