You could try going to about:config and setting browser.newtabpage.activity-stream.newtabLayouts.variant a and b to false.

Do you have steam running? Lately it’s been blocking sleep after even just sitting in the tray for me. This is on arch kde.

It is a bit odd to set up since the selector only shows the device and not the output. You might have to plug the headphones in before you choose and set the preset for headphone output. This is what mine looks like.

Doesn’t easyeffects preset autoloading already offer that? I have auto-mute off since I leave the headphones plugged in all the time, but switching output manually triggers my preset change.