It's been a while since KDE started working on Plasma Login Manager. It will officially arrive with Plasma 6.6, scheduled for February of this year, and when the time comes, the different distributions will have to decide whether or not to implement it. In Plasma 5, the project switched to SDDM, which most distributions use today, but Plasma 4 used KDM. So, we're not wrong when we say that there's a change in the login process with each major update. Among the first to use Plasma Login Manager will be... Fedora 44.
Among the many differences between Fedora and Ubuntu is how each project updates its software. While both release a version every six months, Ubuntu maintains much of its software and updates it along with the rest of the operating system in the next iteration, whereas Fedora updates almost everything that isn't part of its core shortly after it becomes available. It has already been confirmed that Fedora 44 will use Plasma Login Manager.
Fedora 44 will arrive in April with Plasma Login Manager in the KDE editions
The timelines are aligned. Plasma 6.6 will arrive in mid-February, and Fedora 44 will follow about two months later. The KDE desktop editions (Fedora KDE, Fedora KDE Mobile, and Fedora Kinoite) will use Plasma Login Manager, and whether it's the first distribution to implement it will depend on the KDE project's decisions.
Currently, KDE works on two different operating systems: KDE neon, based on Ubuntu and a "normal" distribution, and KDE Linux, an immutable distribution that is currently in alpha, so it shouldn't be considered a standard distribution. If KDE neon delays the implementation of Plasma Login Manager, Fedora 44 will be the first.
Fedora's use of PLM is now a proposal, with the intention of "continuing to provide the most up-to-date and highest-quality KDE Plasma experience." The transition is expected to be seamless for users, and the only change, if any, will be the switch from SDDM to PLM upon upgrading to Fedora 44.