Depends on what you mean by replacing DAZ Studio.
There’s Blender, but it’s like going from training wheels (DAZ) and jumping right into Formula 1. Blender is very powerful and can do everything Studio can do and a million times more. And it’s free. But it’s got a learning curve.
There’s Unity and Unreal Engine. Both are game engines primarily but they are being used more and more for rendering stills and animation. Again, they have a learning curve too. But they’re free.
Have you tried installing DAZ Central? It’s DAZ 3D’s replacement for Install Manager.
It’s much more intuitive and easier to use for new users (which is why DAZ is pushing it so hard) but us old-timers really don’t like it much because it’s too limiting. But for someone new it’s pretty good.
But here’s a secret. You don’t NEED Install Manager.
You can manually download your purchases and manually install them. It’s how we all used to to do it before Install Manager came on the scene. Back in the day DAZ used to supply separate installers for each product so we all had to install products manually.
And you can still do it.
And besides, it’s not like Renderosity has any support for DAZ Install Manager so if you ever want to install purchases from there you’d need to learn how to install products manually anyway.