Use a cloud storage provider like https://drive.math.uzh.ch, https://drive.switch.ch or https://dropbox.com.
- Create a folder 'todo' on your cloud storage with a file 'todo.txt'
Start on thinlinc 'Applications > Office > QTodoTxt'. Open your todo.txt file on your cloud storage:
On Android install simpletask nextcloud (or dropbox) > choose the synchronized todo.txt file.