In mid 2019, we flew into Florida, set up our domicile in Crestview, FL at the Okaloosa Co Office (both DMV and residence/voting) and it took less than a day. We're using Myrvmail.com as our P.O. address (they also handle Good Sams mail). You don't need to be in Florida any length of time to establish the domicile. You do though need to switch your address and banking/credit card accounts to the new Florida address prior to going to get the licences, etc... to show monthly statements that you've "moved". Used to be good info on Escapees website showing how to set up a domicile.
In fact, we were just in Crestview to switch our Montana registrations to Florida. It was a longer wait this time at the DMV office and found out you can set up an appointment in advance. Feel free to call the DMV in Okaloosa Co because I found them to be very helpful.
Oh, you can also establish the Domicile and get drivers licences w/o registering a vehicle/s in the state.