Play a clone of Tetris
Tetris has suggested efficacy in attenuating development or severity of trauma and it seems to have a beneficial ongoing cognitive effect also.
Don’t get Tetris™️, get a good paid version that lets you buy it and doesn’t show ads or track you after buying.
I haven’t done much with it yet but I have Termux installed on my phone. Termux is a free and open source app that, while it’s very limited, allows you to run Linux applications on an android phone/tablet. So far the only things I’ve done with it was that I ran neofetch and I used ciso to compress some iso files into cso files, both of which were just to test it out and get used to using it. I do plan on enabling and trying out X11 at some point but android prevents Termux from having hardware acceleration and the amount of software available for non-android Linux distros is very minimal, so I have no idea how useful it would be.