If you've tried to open a local html file on the lab machines, you may have noticed that it opens in oxygen. This is a mistake. I've made an adjustment in the next version of the hcmc-desktop package to fix this, but for existing accounts you'll need to remove a file in your home directory to reset things. The file is at:

~/.local/share/applications/mimeapps.list

Once deleted, log out and back in, and you will get the default settings for the machine.