Love elliptical but it seems to be causing achilles issue?

Background - So, I had a foot injury over a year ago, and ended up in an aircast boot for a while, and on crutches for a couple of months trying to get this to heal without surgery. However, a second mri finally showed that there was actually more going on than originally thought, and nothing (tears, etc) had healed despite everything tried. My dr finally recommended surgery, which I had at the end of May. I still have some pain from this, but it is very minor compared to those months before surgery, and my calf muscles in that leg are finally almost back to normal. I do not regret having the surgery now. When the injury first happened, I was determined not to ever have surgery, and regret that now.

Since I started going back to the gym at the end of August, I have been doing mainly the elliptical machine because it stresses my foot less than the treadmill. However, since mid-October, I have been having pain and discomfort in the back of my heel and sometimes kind of up the back of my calf. While I am on the elliptical, it doesn't hurt much, but the rest of the day afterward? Very bothersome. It seems like it should be Achilles tendon related.

If so, I am confused. . . I see recommendations for elliptical when it comes to Achilles. It is definitely better for my other injuries/surgery, so I am also upset that I have to worry about this, whatever it is.

Not sure how to exercise. I don't have access to indoor pool right now. (Swimming is one of my favorite sports, and it would be ideal.)

Thanks.