This is a non safe for work, as in lewd, instance.
It’s safe to assume that anything you see here will be lewd.
Just letting you know. If you view the content and then pull a surprised pikachu when you see big anime tiddies, Judy Hopps getting railed or some furry vore… Then it’s on you.
Should this popup continue to show up, you may want to enable cookies or disable privacy focused addons on your browser, I assure you we won’t track our user.
Should that fail, some users claim they got rid of it by hammering the ok button.
You say this machine is headless. Is it at a remote location? If not, is it feasible to connect it to a monitor an keyboard for a few minutes? If so then you could logout, switch DE, and then log back in. That would hopefully set the DE you prefer as user default.
If that’s not possible, then some of the solutions discussed here might be applicable.