Adding my thoughts.
Agree the heart rate monitor is quite useful. Nice to have confirmation that you are working at optimal levels. No more guessing.
I have been doing sprint work on a track. You just can’t do it well on equipment if you have to constantly change settings.
I am lucky that my gym has an indoor track and weather is no longer an issue. The golf course is a good idea for the grass. I have a weak ankle that twists easily and uneven ground can put me out of commission.