So when it comes walking, I was in the same situation few months ago. I was never into sports and stuff. But this time I took the red pill ( given to me by wife) and went to a gym. It made feel really really good. I was very surprised.
Also on the walking, why not get a wearable device ? Ie a watch ? They obviously have privacy concerns but I have one that’s not depending on android ecosystem and this garmin is never connected to Wi-Fi