If Seth_h’s method doesn’t work (more than likely he is correct) possibly when you removed --yes ended up with wrong number of spaces. Found link for PPA for KiCad: 5.1 releases where you can check this. Never know just another idea. I’ve chased similar issues when copy and pasting ending up with difference created by editor I was using on a different installation. Seth helped me on my installation questions on 20.04.