Given the limitations (that you describe in other replies) I think you've got a good list.

Regarding podcasts, this could be a great time to experiment with new ones & decide which you want to listen to longer term.

Perhaps there are some short activities of value to you, such as Anki (assuming you have a smartphone), mentally reviewing your memory palace, or mindfulness exercises. Mindfulness exercises on public transport may seem a little odd, but the distractions may make it more effective as exercise - just be patient with yourself.