The branches diverge over time, at a certain point, it becomes non-trivial to backport changes from master into the release branch. This is also why NixOS will probably never do a 4-5 yr LTS. That’s just too much upkeep, and probably making in-house patches for stuff to still build.
Yes, but I think we just have to do the practical thing about what we are supporting. Most distros don’t ship with 17 desktop managers, 34 window managers, and 60k+ packages. One of the reasons why I was proposing the delay to YY.05 and YY.11 release dates was to help align the releases with “good points in time” for desktop managers on unstable. Which constituted the most “in-house” work for 20.09. In this last release, plasma was the biggest pain, as we were shipping systemd 246, a mix of qt 5.12, 5.14, and 5.15 with plasma 5.18.5 which really shouldn’t exist together.
Shipping plasma 5.19 could have been an option, but it would have been EOL a week or two after the original target release date, and that’s awkward in case there is security issues, 5.18 is an LTS so we can rely on upstream for providing patches, but not for being compatible with things like the latest systemd. Moving the release date to november would mean that we could have packaged plasma 5.20, and kdeApplications on master before ZHF would start; and the 5.20 plasma release would have been supported for the majority of the 20.09 NixOS release. For gnome, we would just be lagging behind their releases by 4-6 weeks, which should be enough time for them to be packaged in nixpkgs.