But I’m fully aware that my frustrations are atomic problems
Are these frustrations solved by layering with rpm-ostree? If so, just go with it. I’ve always layered over a dozen or so packages and it has worked out fine; it’s defaulted to automatic upgrades in the background, so you don’t feel much of it anyways.
I just recently learned that openSUSE users also have a lot of stability due to btrfs snapshots, so maybe that’s really the feature I’m looking for. I don’t know much about it, honestly.
I love openSUSE and what they do with Btrfs snapshots and Snapper.
However, in terms of ‘robustness’ and ‘stability’, I don’t think anything currently out there can hold up to Fedora Atomic, Guix System and NixOS. This is just by design; the leap from traditional to atomic, then reproducible and finally declarative ensures that issues related to hidden/unknown state, accumulation of cruft, bitrot, configuration drift are left behind in the past. If Btrfs snapshots + Snapper would have been sufficient, then openSUSE themselves would never have desired the creation of openSUSE MicroOS (i.e. their attempt at an ‘immutable’ distro) in the first place.