I’m guessing the Paris apt has wood floors/ceilings? The biggest issue for using the trainer will be rhythmic vibrations for your neighbors, so a pad and wheel-off trainer would be helpful as you’ll bounce less.
A proper spin bike helps here too as it won’t flex as much and has a smaller footprint. This is a good opportunity to score a Wahoo BIke, but any bike will do with a PM and you swinging your own resistance lever. I think a Keiser M3i would be among the smallest
With respect to space, If you can keep the rear wheel on, you won’t leave a grease mess around the apt, and not have to store the rear wheel somewhere. The front wheel isn’t that much of a mess. Your goal would be to reduce the bike’s wheelbase for static setup.
For smart trainers, I would think something like Wahoos new roller system would be best because you can keep the rear wheel on and it’ll store easily. The smallest footprint would be a PM the feedback sports one https://www.feedbacksports.com/product/omnium-portable-trainer/ or Minoura FG542 | MINOURA JAPAN . For wheel-on, the Tacx would have the smallest footprint. Keiter makes a fork stand to get the front wheel out of the way.
Let me save you a lot of shopping though… The Most Space Saving Stationary Bike @ SharperImage.com
