Off the top of my head, the top five simple/ish exercises I’ve stuck to are the following:

(1) running (including running in place indoors or ’round my living area, preferably with my favorite music tracks playing);

(2) YouTube whole-body workouts with or without free weights;

(3) rowing machine workouts (my go-to during the 2020 pandemic lockdown);

(4) going to town on my air bike (LOVE it!), and last but oh-so-definitely NOT least

(5) rebounding (LOVE my rebounder & it’s my go-to for when even my air bike can’t release massive pent-up stress!