Sort of. There isn’t another platform to migrate to at the moment. But this link explains how to self-host your data (PDS) https://atproto.com/guides/self-hosting
And in general, because of the way the protocol works, you could easily build a new app and just use the data that Bluesky wrote. So another platform wouldn’t even need users to “migrate”, since it’s “being your own data”
Just because BlueSky isn’t federated doesn’t mean it’s (totally) centralized. It uses the AT protocol which means user data lives in a separate place than the app itself. While the BlueSky app is centralized all the user data (your posts, likes, etc) live in a separate place and can be self-hosted. This means that if BlueSky went bust or something, users could easily just move to a new platform that someone would inevitably create and all of their data, likes, follows would all be there.
You could try getting a Chromebook and installing whatever distro you want on there? I know it doesn’t avoid the pre-installed spyware, but at least it’s free so you’re not loosing money paying for a license. And Chromebooks these days are made in a wide range from very inexpensive to sorta-premium.
Maybe you can be the one to build it!
My guess is that nothing yet exists because A) the official app is generally pretty good and B) Bluesky is pretty newly popular so the demand wasn’t there yet