How about a walk around the block once a month?

I struggle with executive dysfunction; when people describe a more aggressive routine than I could manage, I just mentally translate the numbers and level of consistency into what's achievable rather than berate them. Their point was: start with what's possible for you and go from there, because you don't need to achieve a certain threshold of activity or knowledge for the exercise to benefit you.

Executive dysfunction is different for everybody. I'm sure GP's comment is well intended, but advice in the form of "Just go DO the thing even if it's small" is about as helpful as telling a depressed person "Have you tried smiling?".

Because it varies, there’s even less reason to be upset. You know there are people whose dysfunction looks more like perfectionism or overplanning and the advice is meant for them. You understand that variance in individual cases means that not every general discussion will match yours.

I mean it can be as simple as playing Pokemon Go.

Anything that gets your activity up will help. Lots of low intensity stuff is probably even more valuable than 20 minutes of moderate effort.