My partner told me about these last week. I think you need to have updated the software to the latest release.
In the accessibility menu, there is something called Motion. You can add 'vehicle motion cues' which add dots to the screen to stabilise it.
I get very severe travel sickness. Can't look at my phone on the train, car or bus but having used this for a week, I've started to be able to at least reply to messages. I picked up my work phone this morning on the train (where I haven't turned this on) and I immediately felt sick so it's obviously doing something!
I think you have to give it a week or so to try it out if you can stomach it!