Removed QtWebKit and WebVfx (HTML5 components) from all builds.
Upgraded Qt to version 5.15.1 on Linux and Windows and version 5.12.9 on macOS. As a result, the minimum macOS version is 10.12.
Updated Linux build to a Ubuntu 18.04 base (glibc version 2.27).
Completely new Windows build based on msys2, and discontinued the 32-bit build.
Migrated Windows and Linux builds to GitHub Actions, and automated builds of AppImage and snap for Linux.

New

Added Invert (reverse polarity) audio filter.
Added showing the job progress in Windows taskbar button. (thanks @lolametro!)
Added converting Text: HTML filters to Text: Rich. This does not retain full fidelity, but hopefully it retains the text.
Added using the H.264 hardware encoder if HEVC not available when Proxy > Use Hardware Encoder is on.
Added Scroll to Playhead on Zoom option to Timeline menu.
Added ability to change position in Size, Position & Rotate by dragging anywhere inside the rectangle while also holding <kbd>Shift</kbd>.
Added rectangle VUI help tips for various video filters.
Added Size, Position & Rotate > Zoom now works in any Size mode!
Added Scroll to Playhead on Zoom to Keyframes menu!
Added keyboard shortcut for Center the Playhead: Ctrl+Shift+P.
Added keyboard shortcut for Scroll to Playhead on Zoom: Ctrl+Alt+P.
Added keyboard shortcut for rich text editor Paste Text Only: Ctr+Shift+V
Added common preset resolutions and aspect ratios to the Add Custom Video Mode dialog.

Changes

Improved Text: Rich filter export on Windows and Linux when display scale is fractional (e.g. 150%).
Improved the performance of the Fade In Video, Fade Out Video, and Brightness filters on multicore systems.
Improved image quality when using Size, Position & Rotate.
Changed Export > Codec > Dual pass to not write a video file for the first pass.

Fixed time rulers hiding on vertical scroll in Timeline and Keyframes (regression in v20.09).
Fixed Crop: Rectangle > Corner radius not exactly the same as in version 20.07 (regression in v20.09).
Fixed a compatibility issue for some systems by downgrading FFmpeg to version 4.2 (regression in v20.09).
Improved the Timeline scrolling speed and smoothness (regression in v20.09).
Fixed Blur: Pad incorrect after splitting clip.
Fixed moving the cursor in filter fields may move playhead.
Fixed Filters allowed pasting filters when nothing selected.
Fixed saving projects to Dropbox on Windows leaves temporary files.
Fixed saving the current stock layout when switching to a custom layout.
Fixed progress dialog appears over the convert variable frame rate dialog when dragging to Timeline.
Fixed dropping file with comma in its name to Timeline.
Fixed delete keyframe button in Keyframes may remove keyframe for another parameter.
Fixed convert dialog for variable frame rate never appears if dragged directly to non-empty playlist or timeline.