Cloud eng with ADHD here. It really varies between 30 minutes to 16 hours, both extremes being rare

Some days I feel I'm getting absolutely nothing done, but also quite recently I was hyperfixating on a project and would continue working off hours with a glass or 5 of whiskey because I was having too much of a blast

However I've been reminded before by my manager that the random chatter and stupid meetings are still part of work, and while there's optimizing that can be done, I shouldn't count them as slacking so eh I guess 8 hours a day it is then.