Entering Edinburgh for the Fringe?

If you’ve been in a country or area on the red or amber list in the 10 days before arriving in Scotland, you’ll need to follow the rules for red or amber list countries.

from https://www.gov.scot/publications/coronavirus-covid-19-international-travel-quarantine/pages/red-amber-and-green-list-countries/

So yes you'll need to stay in Croatia for 10 days to avoid quarantine in Auld Reekie

It's odd that Croatia is green and Poland is amber, given that the current rolling average new-infection rate (per million of population) is more than 10 times higher in Croatia than in Poland. Poland's infection rate is currently extremely low. And the rate of growth in Croatia is about 1-1/2 times as high as it is in Poland. I guess there are other factors being considered, but I'd be concerned about whether the Croatian window would be slammed shut before I made it to Scotland.

Sorry, I think Ramblin is wrong - Americans aren’t permitted to enter the U.K. for tourism purposes, irregardless of where you have spent the previous few days. These rules may change, of course.

Jennifer do you have a reference for Americans not being allowed to enter the UK for tourism? All I can find is that as the US is on the amber list, they need to quarantine for 10 days, which would discourage most tourists.

Apologies - Ramblin is correct - this has now changed, so you would have to have a negative Covid test within 3 days of going to Scotland, pay for more tests on days 2 and 8 and isolate for 11 nights in Scotland, (which means not leaving the accommodation for food or exercise). It’s designed to deter people from coming here.