I have flown a lot indoors. It is fine. Just a few things to watch out for.
In a way it is really easy when you start very still air, just concentrate and stay close.
Now the bad part. Because it is so easy it will make you relax and all of a sudden you will hit turbulence from your own MR. You actually can start a small vertical or horizontal tornado, and if you are not used to flying atti this can be a problem, you have to react fast, but not over react.
I would practice somewhere cheap first, like a school gym. Don't use GPS (Pmode) at all even if you get the satellites you will most likely loose them soon.
I had a fun experience last winter I was demoing my S800 with Zenmuse to a crowd in a school gym, with the video I shot on a screen they could see. Well the S800 weighs about 17 lbs so a lot of thrust is needed to keep it up, this does fill the whole gym with unpredictable air currents. Anyway I was fine, the weight also makes a big drone more stable, less susceptible to turbulence. I was flying all around and shooting the audience.
Now the funny part was one of our club members also demoing flying 3D with a very light 3D fixed plane took off and it became completely uncontrollable in the S800 turbulence, and of course he crashed almost immediately. 2 others tried as well same result. I was just happy they did not get sucked into my S800.
Like I said practice a bit in a large garage or a gym before flying somewhere expensive. It is really fun, my first flights with my P3P were actually in my kitchen. But I have a lot of time with both MRs and model Helis, and often fly those in very small spaces.
You may even consider buying a cheap small quad to practice indoors, it will give you confidence and skills that transfer to larger MRs.
And concentrate more your flying than on controlling your gimbal, you can always make the video pass again if you were jerky, but if you crash into something well...