I would say swimming and biking and other no impact activities, and do what you can unilaterally on the other side and work on upper body and other weak areas. I'm no physical therapist so take my suggestions with a grain of salt.
Many years ago as a division 1 college runner I broke an ankle.
Swimming was all I could do. I was terrible at first. Swimming a length was exhausting. Got pretty good after a month and when I was able to run I felt an improvement in my breathing aspect of cardio but legs just a little longer to come back.
So swimming will keep you in shape as long as you do as much or more than what you were previously.
Good luck on a speedy recovery.
I tore my achilles a couple years ago and needed to get in shape for a hunt. Picked up an aqua jogger belt and between that and regular swimming laps was able to keep up/improve my fitness.