These replies are unhelpful and off topic. Author asked for technical resources, not a bunch of opinions about why they are wrong to want this and what they should do instead.

Inevitably other people besides OP will be curious about things to do during their commute and might stumble in here with less specific criteria.

Inevitably other people and OP will not care about off-topic things

If a commute takes 1 hr and that is a time of day when you typically have peak productivity/ mental energy then one is hardly likely to want to just sit there in silence. Do you not think that if you were in prison you might want pen and paper at least?

Well, that might depend on the commute. I'm on the train from 8:20-9am, and I've not yet had coffee, so there's no productivity to be heard of there, and at 5:20-6p the productivity tank is definitely empty.

Perhaps the morning side could, if I were awake. Although, on the afternoon commute, I read stuff such as on HN because I am mentally spent. (Though if it's too rigorous, like a deep CS paper, that might get passed over.)

"Why your brain needs more downtime" https://www.scientificamerican.com/article/mental-downtime/

Maybe s/he already does this before or after the train ride.

A lot of us already do, however audio resources are handy so eyes and hands are free to do even more healthy things like jogging.

To add to this, try meditation too. It can be done while sitting and with the noise around you on a train, and you don't have to look odd by closing your eyes (though you could pretend you are sleeping). However I find it is most comfortable in a private place. I usually listen to music or try to read if it does not make me nauseous, but nothing to do with my studies.