I went thru A foot surgery last year, bad bone spurs. Crushed a couple bones in foot 5-6 years ago..never went to the Dr so I horrible bone spurs..they shaved, cut, and screwed the bones in that area back together.
When the Dr. allows cardio again, I had to wait till my stitches were out. I used an echo bike and then later as it was easier to stand on it a ski erg. 1st couple times on the bike it was arms only. I also took the time do a lot of band work, Is, Ys, Ts, to build up the stabilizer muscles in my shoulders/upper body, until I could start lifting heavy again. Rowers are great too but thats later after its healed some too much load on my foot at 1st. I push hard with my feet on a rower. Some days will feel better than others adjust your workout according, but keep at it. I am pushing 50 so it took me better part of a year to get back to 100%. I was not expecting how quickly the stabilizer muscles in my ankle atrophied being in a boot for 3 months. Getting that back took the longest.
Good Luck!