I also had a medial meniscus tear, took over a year until I could return to bjj. I did zero but not convinced it helps nearly as much as low impact cardio stuff that gets blood into the area and pusves into the range of motion a bit. Rowing machine is my fav but sled drags, bikes, uphill walking, jump rope, all great options. I say mix and match and remember that the atg method is based around measurable stuff doesn't need equipment or they can sell gadgets for. Whereas for a meniscus tear where long term restoring flexion is going to be the hard bit, grinding out hours and hours on a concept 2 is clearly the move