Use a vpn with a Eu server. More sites like google will show a cookie popup with the “reject all cookies” option.
Reject all cookies if it exists. Otherwise accept cookies and then click on the :
shield icon > cookies and site data > delete (trash icon)
This is super useful when you want to read an article on some news website and it shows a cookie popup.
I’m not sure there’s a way other than manually, maybe you could set multiple timezones in the clock app and check the one you’re in