Well, soft tops suck in the winter...so, suck it up.
What I do on mine is to coat them with a teflon/silicone protectant inside and outside.
Some are not supposed to be used inside, so look at the labels.
It helps the snow and rain to slide and/or bead off w/o sticking...so the plastic stays cleaner and has less to freeze up on it.
If its dirty, it catches moisture, and you get frost and or frozen coatings, etc.
DO NOT hit it to loosen the snow/break the ice....it can crack the plastic when its cold enough.
Do not scrape the ice/snow off...it scores the plastic.
Covering the top with a tarp, car cover, etc...works ok, but you need time to get it off/put away, etc.
My last two jeeps, I did the dual top option for this reason...its way less expensive to get the second top that way too.
Prior to the '90's...well, lets just say I saw some plastic die.