If you load AudioThing Lines VST3 in VCV Host FX it crashes, either instantly or after you touch a control in the AudioThing Lines window.
The VST2 version works fine.
I have communicated the problem to AudioThing, and I’ll log a quick bug on the Rack support page.
But if you want to use Lines, just use the VST2 version which works perfectly.
UPDATE: Carlos from Audiothing says they’ll look at the crash next week. I’m a big fan of VCV Rack support, but Audiothing are very responsive as well. Also, Carlos said someone else reported the VST3 crash in Rack, so I bet whoever that was is on this forum.