This gets a bit less Greece-specific but ......
Has anyone used the Emed test for US re-entry?
https://united.emed.com/?fbclid=IwAR0TmGRsQvZVxzCbYPujWF0C7KB8Oj3Q1nLBDfUL 4H0PfsDISClg5X52Q0o
got an ad from United about buying this test before departure .... might make it easier than running around Chania trying to find a testing site.