After using Fedora Atomic for around a year, I've switched my mom over from Linux Mint. Since then a few years've gone by and there's been no issues with automatic updates failing or not applying. That's awesome compared to regular issues with dpkg errors because of shutdown/power loss while updating.

Obviously release upgrades still require manual intervention, but that's an hour once a year for updating and testing if everything works as it should.

Personally I've switched to NixOS, because even with ublue image-based OS aren't great for configuring window managers. In general, image-based OS are especially awesome for long-running, low maintenance systems. I wouldn't want to use an OS which doesn't provide some kind of rollbacks anymore (btrfs snapshots is the minimum).

Edit:

Do you feel it's worth it to learn the nuances of their use?

Fedora Atomic is almost identical to regular Fedora, the difference is mostly how the root filesystem is managed:

The former are files from rpms get copied to an ostree image, which then gets mounted as the root file system.

For the latter dnf copies files from rpms to the root file system.

[...] did you manage to properly run AppImages [...]

They always worked flawlessly on everything except NixOS (because of no FHS-layout). Through distrobox they should work on any distro.

[...] trying to install Outline VPN [...]).

These kinds of not properly packaged apps are a big issue with ostree based systems. VPN provider apps need to be natively installed and usually aren't available in repos.