You'll need to fabricate a soft rubber cushion for that Shark fin antenna. I love my 2019 roof sat antenna which is has no fin when cover's on. Some folks like the shark fin look, but they're becoming to look cheap.
If you can find one cheaper, the car cover my dad had for his 2013 mustang fits my 2020 just fine.
Unless you are buying some super tight fit cover I highly doubt the shark fin antenna is going to do anything to it. Certainly has been no problem on mine.
I would suggest being careful when putting it on and taking it off so as not to drag a rough, outdoor cover over the narrow shark fin, you could wear off some of the clear cloat.