Quoting John Nilsson:

Hello, privyet, I would like to go Donbass/Donetsk and wonder if there are any special rules or conditions that you could tell me about. About visa regulations that is. Thank you for your reply. John

Good day,

Thank you for your message and request.

Entry/exit to Donbass/Donetsk is only possible through Russian Federation.
They have visa free regime for all citizens.

What you need is to obtain Russian visa to enter Russia first and to have a passport when entering and leaving Donbass/Donetsk.
Please, note that your passport will be stamped and you will have some problems entering other territory of Ukraine in future.

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Sincerely yours