I figured it out! Just need to remove the cinnamon configurations and reload the KDE Browser settings:
rm -rf ~/.config/cinnamon
kwriteconfig5 --file ~/.config/kdeglobals --group General --key BrowserApplication "firefox.desktop" #this example sets it to firefox. Change this to your favorite browser.
Source: KDE Plasma 5 - reload kdeglobals or set default browser via command line