I started doing ballet floor barres, barre and (when I'm brave) a bit of centre practice with a couple of Youtubers - Lazy Dancer with Alessia and Kathryn Morgan - during the first lockdown. Both are ballet dancers, moved to teaching, and focus on proper alignment, posture and technique. While also being fun and relaxed! I have taken part in the occasional online live class with Alessia but mostly I just do these at home, anything from 15 minutes to an hour. The stretching ones to prepare for splits I often do in front of the telly with the volume down on the laptop.
I'm in the best shape of my life and lots of the niggles I used to have - tendonitis, plantar fascitis, dodgy hip, dodgy knee, pinched femural nerve - have vanished. Ankles, calves, core, glutes are stronger and my balance and posture is much better. You really get to know where your body is stronger/weaker and notice how effectively (or not) your muscles fire up together and how to get less-used ones, like hamstrings, to contribute their fair share.
So if you want to try for free, start with YouTube, is my advice, and then maybe progress to an actual ballet class for beginner adults?