Whenever I use Muon discover, I cannot navigate with the arrows on the sidebar. I have to scroll with the sidebar itself. The arrows are present, and highlight in blue when I hover above them, but they do not work when I click…any reason?
Seems to be an issue with the qml backend used by Muon. Did you upgrade to the latest muon package ?
I thought so - basically I got into Muon package manager and did a “full upgrade,” hit apply changed, 214 updates were applied, but still seems to be an issue.
which version of muon is that?
I simply did:
sudo apt-get --purge remove muon-updater
no more issues! 
Version 2.1.2