The #FedoraAtomic project brought us the #uBlue project, which is an immutable operating system for ordinary users, which is cool. It is the basis of many new immutable distros.
But, if for some reason you require a #Debian / #Ubuntu base, then look no further than #VanillaOS. With AptX you can install RPM packages if necessary as well, as a toolbox/distrobox alternative... or wrapper?
I might need to test it myself...
Vanilla OS 2 Orchid - Stable Release - Vanilla OS
https://vanillaos.org/blog/article/2024-07-28/vanilla-os-2-orchid---stable-release