Linux, but not Open Source, u-he's new synth Repro-5 public beta is now available. I installed it and give it a quick try for now. Sounds great. Repro-5 is the Sequential Circuit polyphonic Prophet synth emulation. From the KVR thread, first page: https://www.kvraudio.com/forum/viewtopic.php?f=31&t=494717 Cheers.