Should I file under FL if i live here all year, but never formally filed to be a resident? From OH, but never returned after separating from active duty.

If you are no longer on active duty, then you no longer have a legal state of residence in OH.  If you reside in FL all of 2020, you are a Florida resident.   Have you had a residence in Florida, do you have a FL license?   Do you intend on going back to Ohio?  

I do own a home in Fl. I do not have a FL license an do not plan on going back within the next few years.

If you lived in FL all of 2020 and you intend of remaining there, you should claim FL residency.   You should have a FL license if you are not going back to OH anytime soon.  Also, if you are a registered voter, transfer that to FL, otherwise, OH may still think you are a resident and expect a tax return.