A 30 day eSIM with 3GB of data covering most of the EU/Schengen area is sold by Airalo for $13. The missing country from that Europe regional eSIM which is missed most is Switzerland; but that eSIM includes the UK, Turkey, Serbia, Montenegro, Macedonia and the Ukraine as well as most of the EU/Schengen countries too. Combine that data plan with a Google or Skype arrangement to call out + WhatsApp on an unlocked eSIM-capable iPhone and I would say most everything is covered where I go without hesitation in Europe (with the notable exception of Switzerland and Bosnia).