As someone with serious concentration issues (unless I'm hyperfocused, I may have undiagnosed ADHD) I found the biggest help for me was cutting out caffeine.
It’s common that folks with ADHD will use Caffeine, it just doesn’t work as well as other stimulants for many people.
I've been drinking at least 2 cups of coffee ("cups" is a fuzzy measure) for maybe 15 years. Maybe I should power through the withdrawal and discover for myself if I've accidentally been undermining my mental clarity and life quality this whole time, instead of giving myself energy and helping concentration as I'd been assuming.
Maybe I just got used to the feeling and have to feel it to start working.