I’m sorry to hear that your injury was so serious, I was hoping for better news after your reassessment.
I’m not medically trained, so of course listen to your doctor’s/therapists. Especially their timeline for letting the surgery site heal before you start bending/straightening your arm.
That’s said, I think you’re going to need to build up or restore your Range of Motion, in your elbow and probably your shoulder. Basically you’ll go through motions until you have tightness or mild mild pain, exercise through that ROM, then gradually build off that.
Elastic type bands (“mini bands” or "micro min bands) are great for that type of work. They deload when your muscles are stretched, great for rehab. Band Pushdowns, band delt raises, single arm band pullovers, band curls. Slow speed, limited range of motion. Gradually building.
Then body building, mind mind connection stuff for the other side. Some of lifting is “skill” or “neural” or learning the moves. I read somewhere that these neural gains can carry over to the non working side when you do single arm stuff.
Sometime in the future, when Doc says it’s OK maybe you could start pressing light light dumbbells for high high reps.