How to enter Ukraine for a foreigner during the war?

Ukraine is an open country, with quite active migration processes of human resources in both directions. Until recently, a foreigner could enter us from the EU with only a biometric passport and proof of purpose and conditions, and from Turkey and Georgia, for example, only with an ID card. And the movement for pre-issued visas was quite lively. However, the times are wartime, so many people in our friendly countries are wondering if it is as easy to enter as in the past.
This issue worries, first of all, those who have relatives in Ukraine and want to pick them up and escort them to a safe place. And those who have expressed a desire to fight the Russian invasion of our territory with weapons in hand, or to help locals with volunteerism. If before everyone was watching the news about quarantine restrictions and were happy to ease them earlier this year, now the country is at war, so there are many nuances about foreigners crossing the border in this direction.
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The simultaneous stay of visitors in the hotel lobby not more than one person per 10 square meters of serviceable area is allowed.
Persons can visit hotels and stay there (outside hotel room) only if they wear respirator or face mask (including homemade mask), so that the nose and mouth are covered.
Hotel guests are obliged to keep the 1.5 meters distance.
Online check-in making in advance is recommended to avoid queues at check-in to hotel.
Meals in hotels are provided through meals delivery service to rooms upon prior order or at hotel restaurants situated inside or in open areas, provided the distance of at least 1.5 meters between seats at adjacent tables.
Not more than 4 clients are allowed to stay at the table (excluding children under 14 years old). Unless these tables are separated by a special partition;
Self-serve is not allowed.