Germany at a secondary school, grades 5–13:
That was about 20 years ago and learning Latin, let alone Ancient Greek, had become the exception even then.
What helps short term for me are workouts, mostly strength training, and playing board and role-playing games with friends (often online), a nice combination of socializing and concentrating on something. On bad days I’m ignoring the news even though I like to keep informed. For long term improvement I’m looking at getting more into Buddhism, which has shown some promising early results. It’s all about alleviating personal suffering, basically a system of therapy so effective, people made a religion out of it. (The religious trappings can easily be ignored and usually are outside of Asia.)
The GrapheneOS installation is ridiculously easy, you basically just click through the setup on their website. And once you’re accustomed to its features, you’ll never want to go back to stock Android.