I would look into getting a Tonal. I got one about 2 years ago and it's a game changer.
It's not cheap. And requires a monthly subscription of $60. But all four of us (I have two teenagers) are able to use it so that's $15 / each vs. a gym membership.
The plus side is that although it's not quite the same functionality as the gym, you can absolutely maintain and build muscle mass on this machine. And it's in your house, and doesn't require a ton of space. There are a crap ton of workouts, from yoga to pilates to functional strength to HITT to hypertrophy and everything in between. Workouts include moves on and off the machine. Trust me, you can get in a quality workout.
You can filter workouts by time and they have multiple series of workouts under 20 minutes.
Given that it's in your house and you can whip out a workout in 20 minutes, it's a good solution for your situation. The machine will schedule your workouts, track your progress, etc.
Again, it's not perfect. It's expensive and if you have time, you can easily do all of this yourself at a gym. I'm not saying it's a miracle. However if you are super pressed for time, it's a real workout that's literally in your house, and it doesn't consume a ton of space.
https://tonal.com/