Congrats! Take it easy…
I’m not allowed to cycle but can use an exercise bike but not a turbo.
I hate this sort of vague advice that seems like they either don’t know what they’re talking about, or don’t give you enough information to help you avoid the actual issue!
I’d want to know what exactly they’re concerned about – Are they assuming a turbo would have a road bike on it and don’t want you in the hunched/aero position that it would give you? I’m sure you could get that position on an exercise bike if you didn’t know you were supposed to avoid it. Do they not like the idea that you might go hard on a turbo, but guess that you’d use an exercise bike a bit more sedately? – big assumption! Or that they don’t want you swinging a leg over the back of a bike on a turbo, but exercise bikes are usually step-through? Guessing they don’t want you cycling outside in case something unexpected happens and you strain something trying to save yourself.
As per scud’s friend, if you’ve got a mtb or a shopper to keep you upright and a a step to get you on/over (a dropper would be very helpful too), that might get you round what they’re concerned about, and let you look at turbos as well as exercise bikes – someone might even be able to lend you one for a month or so. Fitting the biggest bum-sofa saddle you can find will let you just sit up and spin “no hands” for a good while. I did that post shoulder op.