https://www.medicalnewstoday.com/articles/cardio-exercises-at-home and other sites offer dozens of short-bust cardio workouts, mostly boring, often tough, hardly sustainable. It was frustrating to push myself to do any of these on a monthly basis. They are useful mostly for

• capture a power-surge
• time-saving
• variety

For most of the workouts below, Goal is to increase (through high intensitivy) the heart rate quickly, for a short window like 5+ minutes. The faster you do it, the more tougher.  For that purpose, upper-body-only is seldom sufficient. Even rowing requires some lower body.

— [d] downstairs .. I often feel better doing it downstairs, but some are easier to do than others
— [f] concentration needed .. perhaps injury hazards. Often requires counting, therefore harder to do it while thinking
— ex: climb Blk155 stairs
🙂 no shoes requried
🙂 minimal time wasted on commute
🙂 chance to bring kids
🙂 flexible intensity but may need more concentration
🙂 no need to keep count
I often feel climbing a slope in a nice outdoor location is more enjoyable

— [d] ex: jumping rope:
🙁 more boring
🙂 more gentle, can last a longer time to achieve cardio…

— ex: jumping jack
— [f] ex: mountain climbers
— [f] ex: inchworms
— [f] ex: squat jumps
squat is much safer and easier
— [f] ex: Screamer lunges
regular lunges are safer.
Lunges around the playground frees me from counting.
— [f] ex: Burpees:
🙂 more full-body than the jumping or squat workouts