I’m Rory, the developer at Fat Berry DSP, a small UK plug-in company. We have ten free plug-ins for Windows (VST3) and Mac (VST3 and Audio Unit), so they should load in Ardour on those systems. There is no native Linux build yet, and I’d rather say that up front.
They are Drum Berry, Fidelity, Mutant Brass, Band Practice, Taser, Tremble, FB-60, FB-985, FB-XD and Copy The Dog, covering drums, synths, brass, tremolo and lo-fi character. Each has its own perpetual licence, on up to three machines, and no card is needed.
Download page:
If anyone runs them in Ardour on Windows or Mac, I’d be glad to hear how they behave.