I use Markor for plaintext notes and TODO.txt files as well, synced with Syncthing. Markor itself is open-source under Apache License, and you can disable netwo

I use Markor for plaintext notes and TODO.txt files as well, synced with Syncthing. Markor itself is open-source under Apache License, and you can disable network access via permission or firewall if you don't trust it.