I tried that site in Firefox and Chrome and didn't get the pop up. It might be geo location based which means I need to use a Europe VPN server location and try again. There are also many ways to detect themes and plug-ins on WordPress and this website shows them, but I had no luck with any of those and the Chrome extension. https://wpbuffs.com/wordpress-plugin-theme-checkers/
Just tried a Europe VPN location and I still didn't see that GDPR cookie pop up.
Do you have a specific link that shows that pop up? I'm just not seeing it at all.