In my experience, the most innovative distributions include NixOS and GNU Guix System (Nix influenced it): determinism/correctness, pure functional paradigm, declarative, atomic, departing from FHS for good, … And they are pretty useful currently: Nix has the most packages, both are declarative so can easily reuse the configuration and apply in infrastructure as code, can rollback, can use for development (basically a way better alternative to Docker), can use in other distributions and Nix even on MacOS… Nix community being generally more practical, agile and flexible, while the GNU Guix community enforcing more correctness (building everything in their repositories from source including all transitive dependencies) and software freedom as GNU/FSF defines.
Other distributions I could include are musl based ones, Clear Linux, Fedora SIlverblue, OpenSUSE MicroOS, and projects like sel4, Theseus OS, but I don’t have much experience with them to describe them fairly. So please lets discourse about innovative distributions and operating systems, those which you have experienced, which you may be excited about.
I’m not sure about Silverblue, but on Fedora desktop I had to manualy add the flathub repository, but it’s easy enough. I found the Fedora flatpack repo had a more limited selection of applications.