I'm working on an open-source Subtractive synth for Linux (and Windows/Mac). VST format. You can find it here: https://socalabs.com/synths/virtualanalog/ https://github.com/FigBug/VirtualAnalog
It's compiled for Ubuntu 18.04. If you need it for a different platform it should be as simple as cloning the repo (including submodules), going into the folder ci, export the system variable OS=Linux and run build.sh
There are no patches yet, I'm waiting for parameters to stabilize before I start building patches. If anybody wants to build some patches once things are more feature complete, please send them to me at socalabs@gmail.com.
Please report bugs and feature requests here or on the GitHub page.
It's still early days, so there are probably lots of bugs.
The UI should be pretty obvious other than modulation. The dice control assigning modulation. The 1 die is for mono modulation, the 6 is for poly monduation. Click the correct die and then drag the control you want to modulate. Click the die on the control to disconnect. Hold shift to move the knob while assigning modulation. Click the die top left or the die you originally clicked on to disable modulation assign.
The UI also has collapsible sections so everything fits on the screen. Click the section names to hide and show.
Let me know if you have any questions.
