Although the highlights are mostly found under the hood, there are new features at Kdenlive 21.08 update as well. The NLE (Non-Linear Editor) with version 21.08 is the first (as far as I know) to introduce SpeedRamping (of course, this function is also possible on other editors, but only indirectly). The speed within a clip can now be controlled with keyframes in order to slow down and speed up movements. See video.
Effects can now be applied to a mask, i.e. only to a specific area of a clip. This feature is a first implementation. The workflow is not yet optimal and at the moment the process comprises 3 steps. An improved workflow should be expected in the coming versions.
This version of Kdenlive now requires MLT7, which provides a more stable and clear code base. (MLT7 lays the foundation for long-awaited features like GPU processing, multicore support, and improved color management, all of which are expected in MLT8 – to name a few).
The automask effect has been removed in MLT7 along with many other outdated and buggy modules, but has been replaced with more powerful OpenCV tools. The region module has also been removed and replaced by the new effect masking function described above. The code base has also been cleaned up and old and unmaintained tools such as the DVD wizard (which has become somewhat obsolete) and the preview compositing mode have been removed.
The code for job processing has been completely revised and now fixes a delay that occurred when importing large amounts of files (hundreds of gigabytes). Scrolling through the timeline has also become smoother and smoother thanks to the changes.
According to the website, it is not recommended to open old projects with Kdenlive 21.08.
The current version can be downloaded as a Flatpak, Appimage or via PPA and as a standalone or EXE for Windows.
Unfortunately, the fade-in / fade-out effect of the Appimage version is currently flawed – the image turns pink and green during the fade. In the meantime, it is advisable to use the Flatpak version where this does not occur (according to the comments on the website).