Im a huge advocate for fitness and diet for people who are having trouble with mental health. Because it gives you something you can nerd out on, control, research and if it sticks its a huge net positive for your life.
Figuring out your macros, setting yourself a step goal, designing a functional diet, doing some basic weight training even with just bodyweight exercises.
It also has the advantage of quite often leaving you tired at the end of the day. I can recommend some resources if you like.
Not just the exercise but learning about exercise physiology, calculating macros, protein quality, eating windows, getting adequate sleep to sustain muscle growth, fat loss and testosterone levels… etc.
I’m my own hobby now.