Foreign nationals of the countries with high prevalence of COVID-19 and persons arriving to Ukraine from these countries are exempted from self-isolation regime on condition of a negative PCR test for COVID-19, conducted no more than 48 hours before crossing the border.
Decision of the Government of Ukraine is here: https://www.kmu.gov.ua/npas/pro-vnesennya-zmin-do-postanovi-kabinetu-ministriv-ukrayini-vid-24-kvitnya-2020-r-331-i-vid-22-lipnya-t120820