Low impact is going to be your best go to swimming/aqua therapy (physiotherapy in water)/aquaerobics and the like are fantastic as you get the exercise while also working against the water but because it's also supporting you there's less chance of damage. If you're not able to access a pool (I wouldn't recommend wild swimming just from a safety viewpoint) then cycling/walking are good options too. Depending on how extensive your osteoporosis is, even the shock of landing on your feet while running can cause fractures - so speak to your doctor before considering something with more shocks. Good luck finding the right exercise!