Freeware - Amalgamated Signals Nepenthe Reverb VST Plugin

https://amalgamatedsignals.com/nepenthe

Nepenthe is a reverb designed to be smooth, transparent, and easy to use. Nepenthe's algorithm is based on the concept of velvet noise. Rather than building echoes with a network of delay lines, it uses a predetermined set of randomly-generated echoes. This is a very simple design, which works well with modern CPU optimizations, so Nepenthe runs efficiently. Nepenthe is open source, and its code is annotated with detailed explanations of the design.