My set-up

On Windows I use the GTD Sync add-on with Freeplane 1.3.15 on Windows. I also use todotxt.net (benrhughes.github.io) by Ben Hughes, which lists and filters my next actions in todo.txt very well. It has an option to automatically refresh next actions from the file, which enables you to see the results of your sync immediately.

I have portable versions of Freeplane and todotxt.net installed on a USB stick, so I can use it on Windows computers wherever I go without the need to install.

I use Dropbox to synchronise the file \todo\todo.txt between systems.

On Android I use Simpletask by Mark Janssen. It has a very comprehensive set of sorting and filtering features.

If you have your own set-up that works well with GTD sync, please let me know on the forum. I will then add it to this page.