I found that sleep quality is the number one metric that determines the level of ADHD sympthoms I experience. I do yin yoga before sleep every day, and have fully quit caffeine. I also make sure to not eat at least 4 hours before bed and to not look at any screens 1 hour before my bedtime. Sleep is absolutely my number 1 priority in life.
Starting my day with some heart-rate elevating exercise is the second most helpful habit. I really got into power yoga during lockdown, I highly recommend it.
Having elevated blood ketones, either through fasting or eating low carb, are the third most helpful tool. My level of focus is just incredible when my body has switched to fats as the main fuel source.
My ADHD is quite manageable this way. I feel like having to work for mental clarity is better for me than relying on amphetamines.