The hardest part is habit-building. So whatever works for you for building daily habits. My plan is to put a calendar on the wall with boxes for habits and check them off with a colored pen. Nice visible reminder of what I'm working on and how I'm doing. I was derailed by a severe cold that I'm still recovering from.

The exercise routine itself matters less, IMO, than building the habit. Some basic calisthenics (bodyweight exercises) would be fine to start. You could add dumbbells or a kettlebell at some point to add weight for a minimum of space.

The exercise I "enjoyed" the most was barbell lifting: deadlift, squat, benchpress, cleans, rows, etc. Starting Strength was a really good read for that, and there are videos to go with them. I also worked with a trainer at the gym for a while to get the form correct. That all requires a fair bit of equipment or gym access, though.