VanillaOS is pretty neat. It has an immutable (kind of) OS, lets you choose which package formats you want to use (flatpak, snap, appimage, etc) and leverages containers (a la Distrobox) and their package manager Apx to give you seamless access to packages on other distros. It's Ubuntu-based right now but the next release is switching to debian.
To be fair, I don't have much time on it. My daily drivers are a chromebook and a steamdeck, but I did dust off an old laptop just to check it out for a little bit.