You can find the latest releases for KDE Frameworks, Plasma, and Applications under the "Announcements" section on https://www.kde.org.

KDE Frameworks

KDE Frameworks is released monthly and includes all frameworks, such as KIO and Kirigami. Every commit to a project under the KDE frameworks umbrella targets the next release. For example, if the latest release is KDE Frameworks 5.43, then a patch for a KDE Frameworks project will target 5.44

KDE Applications

KDE Applications is released three times a year and includes all KDE apps (Except for Discover, which releases with Plasma).

Patches to KDE Applications that involve string changes, new features, or major code changes should target the next major KDE Applications release. For example, if the latest release is KDE Applications 18.04.1, then such a patch will target 18.08.0

Patches to KDE Applications that involve minor changes or bug fixes that do not involve string changes can go into a bugfix release for the latest KDE Applications release. For example, if the latest release is KDE Applications 18.04.1, then such a patch will target 18.04.2

KDE Plasma

KDE Plasma is released three times a year and includes everything related to Plasma (for example Discover).

Patches to KDE Plasma (so even Discover) that involve string changes, new features, or major code changes should target the next major KDE Plasma release. For example, if the latest release is KDE Plasma 5.12.1, then such a patch will target 5.13.0

Patches to KDE Plasma (so even Discover) that involve minor changes or bug fixes that do not involve string changes can go into a bugfix release for the latest KDE Applications release. For example, if the latest release is KDE Plasma 5.12, then such a patch will target 5.12.1