Yep stretching over a period should help unless you have foreign bodies locking in the joint etc. but definitely try:
Knee to wall stretch (as per the test procedure, hold for 30seconds 10+ times per day (not all at once, just throughout the day))
Calf stretch (normal calf stretch)
Calf stretch turning the foot in towards the front foot (when leaning forward against a wall etc.)
Calf stretch off a step (front of foot on a step and hang the heel off)
Joint mobilisation w/ your physio with active and passive dorsiflexion etc. as described in other posts.
Skateboard / Rolling foot forward and back as far as the ankle will go while holding the heel down
You can also try some active exercises which require joint movement to help loosen the ankle (try non weightbearing and progress) i.e. elastic band pushing your foot out and then bringing it up (with and against resistance, so band being held by you and band being held down past your foot while lying) to hydro (calf raises on a step in a pool etc...) then weightbearing (squats, single leg squats, walking lunges with a long heel on the ground hold) .. when you get some range back and symptoms ease hit me up I can actually specifically prescribe you some exercises...
In terms of surgery, properly conservatively manage it first, if that does not work get a specialist to r/v your investigations, they will tell you if surgery is required or not. No surgery is ever a "small" surgery, so take it very seriously if you are considering the option. I would suggest further conservative management... and go see a good physio!