A good source of information about current rules of crossing Ukrainian border, self-isolation requirements, list of “green zone / red zone” countries, etc., available in English:
They also provide links to some insurance companies where you can purchase your entry insurance policy, which covers COVID-19 treatment and observation. As well as an insurance policy for travel abroad.
On this portal you will also find the information about how to install and how to use the mobile application Dii Vdoma for those who have to stay self-isolated after arriving in Ukraine.
It was created with the support of the State Agency for Tourism Development, the Border Guard Service of Ukraine and the representatives of the Ministry of Infrastructure, the Ministry of Health and the Ministry of Foreign Affairs of Ukraine. They update their information daily.