Are universal travel adapters safe? Do they have surge protection?

Most do not. Several of the highly-rated universal adapters explicitly state they lack surge protection (which is why they're often cleared for cruise-ship use). At least one r/digitalnomad thread documents a Ceptics adapter failing under a surge. If you're traveling through regions with unstable mains, plug a surge-protected power strip into the adapter rather than relying on the adapter itself.