If you’re trying to use vmpk to control something in SC - you have your MIDI ins and outs reversed in vmpk.
You should connect Output MIDI Connection to SuperCollider(0) …or whichever one you prefer… instead.
The screenshot of your current MIDI preferences in that pop-up menu, you’re currently listening for MIDI signals coming from SuperCollider, and outputting MIDI signals to SonivoxEAS.
Also, if you want to control SC, you should likely turn disable that middle checkbox: Enable MIDI Thru on MIDI Output, just in case.
Unfortunately I’m not on a Linux build, so I’m not quite sure why that is. Certainly seems the issue is in vmpk, especially if it’s crashing.
Also odd that in the screenshot in your first post with all the patched up MIDI modules there is no VMPK output anywhere, just that through connection. Could it be that VMPK is just software for piano sounds, not a piano-style keyboard controller?
The command line utility “aconnect” allows to connect and disconnect the virtual MIDI cables between any ports, being hardware interfaces or applications. A nice GUI utility for doing the same is QJackCtl.
Maybe the port has to be ‘created’ first? Purely guessing at this point though as I’ve never used this software.