I don't think there's anything at all that can make indoor exercise less than a drudgery. Music, movies, books help, but it's still a drudgery. It's just the way it is.
C'mon, spring!
There's something, but it's rather high-tech, and therefore expensive.
Actually, it may not even exist yet. I'm talking about immersive artificial reality games and exercise programs.
The simple version is a feedback system for a treadmill or bicycle exercizer. As you "move," the scenery changes. If the displayed scene shows an uphill climb, your treadmill should adjust to make the exercise match.
The next level might include a wearable helmet with a visor display, showing the same scenes. To make it more realistic, it should have 3-D, and respond to the motions of your head. When you turn your head to the left, you would see the left side of the trail, and so forth.
Now, beyond that is an immersive chair, jacket, or "suit." After you "suit" up, you begin "walking" through an artificial reality, hopefully one that changes every day, unless you want to re-visit your favorite garden.
As you can see, this type of equipment is open-ended as far as how realistic or entertaining it could be.
I'm looking forward to it. I just hope I can afford it when it becomes available.