RJ Studios has updated their True Mid/Side, Mid<>Side Channel Extractor to version 1.4.0 with additional algorithm improvements. They say:
The improved algorithm provides greater separation detail with less smearing and background echo producing much cleaner and "drier" stems.
This update also patches a VST3 compatibility issue reported in Ardour and Harrison Mixbus.
True Mid/Side is a plugin that extracts the "phantom" center and stereo sides from a stereo mix, track or bus.
Price: $39.95 at the RJ Studios webstore while the update is free for all current owners. Free 14-day trial demos are available for download at RJ Studio's website.
True Mid/Side is a 64-bit plugin in VST, VST3 and AAX formats for Windows PC and VST, VST3, AAX and AU formats for Mac OS 10.11+ on Intel and Apple Silicon.